Future Energy Sources 3.1.5 Hydrogen from Biomasses

Again, the SOFC will do the reforming and complete oxidation of ethanol directly as it produces electricity at 55% efficiency. The process also produces heat at 850°C which can be used in many ways to increase the overall efficiency to between 80% to 90%, maybe even more. One more little tidbit, the SOFC is not limited to alcohol, it work with methane (produced in septic tanks), propane, natural gas, any liquid alcohol, syn-gas produced from biomass, oil or coal, and hydrogen produced by any means. One more thing, alcohol can be and is produced by farmers and individuals to supply their own motor fuel. The process is simple, natural, well known and developed, and does not require use of the food part of the plant.

On the issue of competition between biomass for food and for fuel it would be far preferable if we could get to the point of using agricultural waste rather that food products.

The same question relates to large users of natural gas such as power plants competing and running the cost up for the fuel that many people use to heat their house. I'd prefer that power be produced using energy sources that I can't use at home.

The 2,5-demethylfuran DMF (http://www.sciam.com/article.cfm?articleID=4AF8E5BD-E7F2-99DF-37013D71D6975B0E&chanID=sa007) looks a little more attractive to me than the Partial Oxidation of Alcohol paper in that: (1) less development appears to be required; (2) the existing fuel use infrastructure could be used; and (3) the issues to be resolved look more straightforward.

The Partial Oxidation of Alcohol process, providing an alternative for obtaining hydrogen at the use point might possibly compete with reforming, but there seems to be a lot more development required and there is still the issue of the cost of the fuel cell it would be feeding.

The use of corn as the base for ethanol production certainly does has food production problems. There is enough arable land in the USA to support the growth of sugar beets, which have a much greater yield than corn. Sugar beets can be grown almost anywhere in the USA, and do not require the best soil either. The final ethanol yield is about 3 times that of corn, without affecting food procuction factors.

Sugar Beets are not as viable as corn, are water intensive, and has a very limited utility as a food product for humans and animals. The production of any grain crop is viable in that it allows an excess of production to be maintained with respect to the food market and as a animal feed. Any excess production for one market, if wisely used, can be funneled into another market to meet demands. Also, Corn is used in the US because so much is known about corn production, water consumption, and fertility, it is a common crop for land application of treated wastewaters (or untreated dairy waste).

The corn stock and ear after the grain is removed has large quantities of starch and sugar remaining which can be harvested with enzymes and boiling. The same is true with much of the biomass waste products.

There are other alternatives though that might be considered as optional sugar sources for fermentation, a more open market for supplies. I know a couple of years back the bottom dropped out of the raisan market just as harvest started, and the fruit was left on the ground since it was not cost effective to spend labor collecting it and processing it. this happens a lot in various markets, some of the fruits and grains when not worth selling for food stuff, might be viable for ethanol production (assuming the labor is not too intense).

Hi,

sugar can be made simply by treating wood (cellulosis) with diluted acid.

RHABE

There are a several points that I think are worth raising here:

1. The important factor with fuel crops is how efficient they are at producing sugars and starches that can then be turned into some sort of fuel. What is important is how much energy is available in the final product minus the energy consumed growing, harvesting and processing the plant material.
2. While it is possible to utilize crops that are surplus to requirements it is a waste of materials and effort cultivating a food quality crop to food quality standards when it is not necessary. If you are growing a crop that isn't going to be consumed then you can use a whole host of techniques, processes and chemical treatments that increase the yield but would render the crop unfit for human consumption.
3. If you do have a dual standard crop it is then important to make sure that unscrupulous people do not use crops that are grown for fuel and are not fit for human consumption as foodstuffs.

It varies with location, weather, the time of year, time of day and a host of other parameters but on average the sunlight imparts about 1 kW m^-2 at ground level. Currently we consume about 500 EJ of which around 435 EJ comes from fossil fuels.

I know this is impossible and unrealistic but for the moment let us assume that we have a perfect plant that is 100% efficient at turning sunlight into energy and we have a perfect climate that allows the plants to grow at fill pace for 12 hours each day. If we make this assumption we can now work out how much are we need to devote to fuel crops as follows:

• Crop_Area = 435 EJ ÷ (1 kW x 43,200 sec x 365.25 days)
• Crop_Area = 15.779 x 10⁹ m²
• Crop_Area ≈ 16 x 10⁹ m ²

Now as I said this is an unrealistic figure as no plant is anywhere near 100% efficient and there are a whole host of components that reduce the efficiency but we can use this as a starting point and then multiply it by the various efficiency factors to give us some sort or realistic figure.

For the moment I will leave it here, but I will do some research on the various crops that may be used and find out how efficient they are at creating fuel. In the meantime you may like to find out something about your local climate, particularly the mean number of daylight hours etcetera that will limit the crop yield.

What you say here, masu, if very true, and sadly so. It is our job, yours and mine, to fix that. As you well know, the human being is, by a wide margin, the most wasteful of all life on earth. Just the simple act of walking several blocks to the store rather than driving the car can save gasoline, greenhouse gas, and other ozone producing pollutants. Simply by changing to florescent light bulbs can save nearly 80% of the energy needed to light our way. Simply switching to steel and concrete rather than wood for home construction will save millions of board feet of lumber (save our rain forests). There are many things we can do to help.

Our industry, and especially our refineries, have been working hard to upgrade to save energy by installing equipment to reduce heat loss. This is done by recovering the heat of process that was discharged at the end of the line and moving it to the start of the process, installing heat exchanges along the process route. I know, since this was one of the things I was involved with while I was still working. But still today, a goodly portion of our oil is used simply to power our energy producing industries. Think of this, a turbine driven electrical generator, running at peak efficiency, operates at about 30% efficiency. The same is true for diesel driven or even steam driven generation. It does not matter which fuel is used, gas, oil, or coal, only about 1/3 of the fuel's energy becomes electricity. he rest is lost as heat, 2/3 of the energy that is 'wasted'.

The research and scientific effort today is to improve the efficiency of our energy conversion. This is why we hear all the hype about solar energy, fuel cells, and wind turbines. These can either capture the energy of our sun (wind is solar energy, too) or it can use existing fuels with far more efficiency. Solar Cells, even at 5% efficiency, consume only sunlight to produce electricity. They main drawback is that the sun has to be shinning, regardless of their efficiency. Thus, even the electric power produced by a 50% efficient solar cell must be somehow stored for use as needed. When one thinks of the electric power needed run an air conditioner, this is a great source of power, since it is the sun's heat that we want to move out doors. But for lighting the baseball park at night, the solar cell's energy must be stored in some way for use after dark. The same is true, too, for wind turbines. The wind must blow (at least 8 mph) for them to work.efficient wind turbines are big and occupy land. Usually, many of today's wind farms are located in the great plains, valuable farm land for growing corn and wheat. Even the grass lands (corn and wheat are grasses) used for cattle is reduced by the footprint of wind turbines.

So, this leaves one last item on the research and development agenda for energy efficiency, the fuel cell. The fuel call has been known for nearly 150 years but was never considered development until the last few years. There are a number of types of fuel cells being considered but, but for the most part, only one type of fuel cell is capable of using all of the fuels of today. This is the solid oxide fuel cell, which can convert hydrogen, methane, propane, light hydrocarbons, and alcohols into electricity at or about 50% efficiency. This is far better than our best mechanically driven power generators can achieve and thus a 40% improvement in savings in the greenhouse gases produced and in fuel cost savings when fossil fuels are used. By adding naturally (normally wasted) produced biomass fuels to the system, even greater savings can be achieved.

May I point out that Siemens is already producing and installing megawatts of their solid oxide fuel cells for powering our factories and for commercial power plants. Acrumentrics is doing the same but on a much smaller scale, producing 3KW and 5KW units as backup power and home uses. There are many more companies who are entering this market, too, here in the USA, in Europe, and in Asia. The solar cell industry is here and is NOW! In the next few years you will be seeing news items and advertisements on TV about all of this coming to pass. The incentives are here now, and many governments are subsidizing private industry to get the ball rolling. I would say that the effort being put into converting to the hydrogen economy is approaching that which sent man to the in the 60's. It is silent for now, but you will soon be hearing about it. One more item to come, too, is advancements with nuclear fusion energy, both for producing electrical power and for the rocket power to take us to the stars. Fusion power is about 20 to 50 years down the road but is coming.

"Simply switching to steel and concrete rather than wood for home construction will save millions of board feet of lumber (save our rain forests). "

Chtank, apart from the above statement your post makes a lot of sense.

Timber is fully renewable and "sequesters" carbon as a by product. It is the management of logging not logging per se that is the environmental vandal. Before the previous labour Federal Government decided to curry favour with the city based greens by closing the sustainable forestry industry in North Queensland Australia, mature timber was harvested on a cyclic basis. The forests were so well managed that the logged land was declared "Pristine World Heritage" and locked up to rot.

The world has not only lost a major source of renewable high quality timber, but entire model has been thrown out as well. So what has happened in the absence of the high quality timbers from Nth QLD? Well the Indonesians and Malays have destroyed Borneo while the misinformed world wrung its hands. Sustainable yeild forestry is possible, proven, desirable and essential.

Steel and Concrete are huge contributors to CO2 production and should be used sparingly (which would cost me my job). Timber can also be much better performing in a structural fire situation as it takes time to thin the timber to the point of weakness but localised heat softens steel quickly and collapse results. Borax treated timber is fire retardant to the point of requiring less protection from sprinklers than steel. One situation I came across in a timber storage warehouse allowed the owners to use smoke detection when they chose borax treated timber instead of sprinklers if they had selected steel. This resulted in a major saving in construction costs.

Steel and Concrete do not grow on trees , when they do I'll revise my view.

Emjay4119,

Please understand that the rain forest of the world are disappearing at an alarming rate. They are being harvested for their tropical hardwoods which bring a very large profit for the lumber companies. These rain forests are unlike our once vast pine forests which once covered a major part of the United States in that they are not fast growing. The pine forests can be replanted and ready for harvest in less than 20 years. However, the hardwoods of the rain forests take more than a century to regrow. These forests are also one of the greatest carbon sinks available to the earth. As we destroy the rain forests we reduce the earth's ability to recover from mankind's introduced extra carbon dioxide. By replacing the clear cut trees of the Amazon with farming is not the answer. You see, the land is very shallow and after just a couple years is depleted to the point that is is even unable to support the regrowth of any thing but weeds and some weeds even fail. This leaves nothing but hard pan earth that traps the suns heat and increases still yet the heat gain of the earth.

Some what of a parallel event happened in USA's history when the vast grasslands of the Mid West were plowed under and exploited for grain crops. The improper farming techniques of the early 29th century directly contributed to the great dust bowl and drought of the 1920's. Today, the great tall and short grasslands that once covered nearly all of the land between the Mississippi river and the Rocky Mountains from Canada to the Gulf of Mexico is all but gone. The same is true of the world's larges known pine forest that covered the souther half east of the Mississippi and the hard wood forest that was north of to Canada. Today we have learn some of our lessons, but I fear we still have much yet to learn. Gosh, man, how can we be so wasteful for just a fist full of dollars?

Sustainable yield forestry does not involve any clear felling. It works on a tree mark scheme where only the trees marked for harvesting are removed. Not only the tree identity is marked but also the direction it must be felled to prevent or minimise damage to replacement trees. The method was so successful that on both Fraser Island and in North Qld the forests were declared pristine when they were locked up.

This scheme was not voluntary. Queensland Forestry officials enforced it rigorously. In short order even the tracks grow over and when there is mature timber hindering the regrowth of the forest it is again harvested, this process takes a period of years. The trees harvested in each cycle were growing in the previous cycle. No sections become denuded at all, basically the dying trees are removed.

Other regions in other states use clear felling techniques for different species, mostly Eucalypts. I have natural reservations about clear felling, but the professionals in those regions notably Western Australia point out that nature in those areas wipes out areas and replaces entire sections of forest for instance the Valley of the Giants where a large stand of uniform age absolutely massive Karri trees occur. Their method involves felling coups and leaving uniform age regrowth to occur. It appears to work but is ugly and possibly open to abuse by for instance planting a single species plantation instead of variegated natural regrowth.

The destruction of tropical forest in places such as Borneo did not need to occur to provide timber. More timber, more jobs, more remnant forest and more wildlife preservation would have resulted from the adoption of the Queensland model universally. The largest portion of the damage has occurred since the closure of the model sustainable yield forests.

When tree mark is used there is no loss of habitat as only a very small percentage of trees are removed at any time. Animals dependant on a fallen tree simply move to the next tree as if it had fallen naturally.

While I am an advocate for preservation of the natural forests, I am forced to admit that even plantation timber is more environmentally sustainable than steel and concrete both of which take huge amounts of energy derived from fossil fuels to produce. We can't avoid using either steel or concrete, but mindlessly replacing renewables with them is only doing worse damage.

Hi Emjay4119,

• The world has not only lost a major source of renewable high quality timber, but entire model has been thrown out as well. So what has happened in the absence of the high quality timbers from Nth QLD? Well the Indonesians and Malays have destroyed Borneo while the misinformed world wrung its hands. Sustainable yeild forestry is possible, proven, desirable and essential.

Many of the so called greenies have with their single minded narrow outlook, done vastly more damage to the environment than if they had left tings alone and done nothing. We cant live without having an effect on the planet, what we need to do is work out how to keep that damage to a level that the planet can tolerate and harvesting timber in the manner you described is part of the solution.

I believe many of the problems we are now facing worldwide are not due to what we as engineers are doing, but rather what is being done by managers that only look at things from a purely short term profit driven outlook and insist on ignoring the advice from the specialists, technical people and engineers they are supposed to be managing.

How many times have you heard management come out with things like:

• "Don't give me problems give me solutions"
• "That's not the answer I wanted."
• "You're not paid to think"
• "Failure is not an option"
• "We can't afford to look at new ideas"
• "We have always done it that way"
• "We are only here to make a profit"

If we, as a human race, are going to survive long term we have no option but to mend our wasteful polluting ways and learn to live in a sustainable way. One of the great idiot statements that managers and accountants bandy about is "sustainable growth". There is no such thing, never has been and never will be. We live on a finite lump of rock called Earth and if we keep growing sooner or later there will be nothing left but us. What we should really be thinking of is "sustainable existence".

Unfortunately, the powers to be and that includes politicians, managers, accountants and so on, are all using a flawed system that only measures success on how much profit is generated over very short time spans. The system we currently use does not take into account the cost of the damage we are doing to the environment. In reality we are subsidizing the use of fossil fuels with the future expenditure that will be required to accommodate the changes in climate and undo the damage done to the environment in general.

What is needed is a complete rethink of the way we measure success, failure and profitability. Since the powers to be have no interest in replacing a system that keeps them in power it is going to be up to us as engineers to do the lateral thinking and come up with the systems, technology and answers that are needed.

Now that's the easy part, the hard part is getting it past the powers to be, who I am certain will do as much as they can to keep the status quo. Nonetheless, I see no other solution to the problems we face and if we stand back do nothing because we feel it is too hard, then we have nobody to blame than ourselves.

Ok, I have had my daily sociopolitical rant, but I am sure you can see what I mean and understand what I am raving about.

Hi chtank,

• Simply switching to steel and concrete rather than wood for home construction will save millions of board feet of lumber (save our rain forests). There are many things we can do to help.

While I agree that we should be utilizing materials like steel and concrete to construct houses it is a little more complex than just working out how much wood is saved. You need to take into the account the amount of energy that is required to produce the construction materials and when you do concrete is many times more damaging to the environment than chopping down a few trees for wood. Steel is not much better as it requires something like 7 tonnes of coal, 2 tonnes of limestone and 2 tonnes of iron ore to make less than 1 tonne of raw pig iron. You then need to look at the energy that is needed to turn it into the final steel products for use in construction.

However, steel and concrete usually produce structures that are stronger and less prone to deteorating and are more easily adapted to high tech energy saving technologies.

• This is why we hear all the hype about solar energy, fuel cells, and wind turbines. These can either capture the energy of our sun (wind is solar energy, too) or it can use existing fuels with far more efficiency. Solar Cells, even at 5% efficiency, consume only sunlight to produce electricity. They main drawback is that the sun has to be shinning, regardless of their efficiency. Thus, even the electric power produced by a 50% efficient solar cell must be somehow stored for use as needed.

Not necessarily. If you had a power distribution grid that covered the entire planet then the areas that are receiving sunlight can supply power to those that are not.

Now I realize a global electricity grid is unrealistic with current technology but if you utilize the existing continent wide grids and utilize multiple technologies like wind, solar hydro, geothermal, wave or any other technology that may be developed in the future you can archive a similar result.

Basically by spreading the generating capacity over a large enough area and utilizing a diverse enough range of technologies you can ensure that any short fall in one area can be made up by the surplus in another area that utilizes a different technology. That then leave things like hydro and geothermal, that can be quickly brought on line and have scalable output capacity, to cover any transient or short tem shortfalls.

The are many advantages to such a system:

1. It can be constructed from existing technology and does not require the massive amounts of dead money involved in developing, testing and starting production of new technologies.
2. It can easily accommodate the use of any new generating technology that may be developed in the future. All that is required is some way of converting the energy from that technology to an electrical form compatible with the grid.
3. Renewable power generating techniques can be matched to areas. For example in a desert region solar panels could be used while near the coast where it is windy wind power or wave technology could be used.
4. The existing power distribution grids would be more than capable of distributing the power. Without going into the complexities the existing grid would actually be capable of distributing around 200% of their current peak capacity.
5. It can be implemented on a piece wise basis and brought on line as each individual generating facility is completed. It can also be easily scaled from household to large generating facilities.

So, in reality there is no technical reason why we can't start implementing such a system other than man made sociopolitical barriers we impose on ourselves. In fact such systems are already available and are being installed in several countries already.

• The wind must blow (at least 8 mph) for them to work.efficient wind turbines are big and occupy land. Usually, many of today's wind farms are located in the great plains, valuable farm land for growing corn and wheat. Even the grass lands (corn and wheat are grasses) used for cattle is reduced by the footprint of wind turbines.

While they do occupy a certain amount of land there is no reason the land around the base of the towers can't be used for agricultural purposes and in fact this is done at many locations. The total loss of agricultural land can be kept to an overall negligible amount.

You can also put wind farms out at see and over the horizon so you don't take up any land or create anything that people can call an eyesore because it can't be seen. There are already off shore wind farms in the North Sea and in reality they are far less of a problem or danger than the many off shore oil rigs.

• There are a number of types of fuel cells being considered but, but for the most part, only one type of fuel cell is capable of using all of the fuels of today. This is the solid oxide fuel cell, which can convert hydrogen, methane, propane, light hydrocarbons, and alcohols into electricity at or about 50% efficiency. This is far better than our best mechanically driven power generators can achieve and thus a 40% improvement in savings in the greenhouse gases produced and in fuel cost savings when fossil fuels are used. By adding naturally (normally wasted) produced biomass fuels to the system, even greater savings can be achieved.

While this is true in reality fuel cells can be particularly pedantic items of technology and are very prone to contamination and damage by impurities in the fuels. They also get very hot and while in theory can operate at very high efficiency in reality when used in applications like motor vehicles where they are coupled with electric motors the overall efficiency is not greatly different to an internal combustion engine with a mechanical power transmission and drive train.

Don't get me wrong, I think fuel cells have a future and there are some applications where they are ideally suited, I just can't see them working well is applications like general transport. You also need to keep in mind fuel cells are not an energy source by themselves and unless the fuel they use is coming from a renewable source you are no better off.

• What you say here, masu, if very true, and sadly so. It is our job, yours and mine, to fix that. As you well know, the human being is, by a wide margin, the most wasteful of all life on earth.

I agree with you 100% in that it is the job of all of us to fix the problem and get ourselves free form our addiction to fossil fuels. Due to circumstances out of my control I am limited in what I can do, but this An Engineer's Look at the Future of Energy blog is my way of introducing the problem to as many engineers as possible and discussing the possible solutions. If you go to the Blog Table of Contents you can see a list of the technologies I have or intend to start threads on with links to threads that have already taken place. If you have a suggestion for a thread please feel free to send me a message and I will gladly add them to the list. While it's is not essential it would be greatly appreciated if you could include any links you know of to sites that have information on the technology.

first of all, concrete is the engineers dream as a construction material. It was first used by the Romans 2,000 years ago and some of the concrete structures still stand. Steel, as a building material, is relatively new but is a common material for tall buildings and otehr heavy load structures. I doubt that the manufacturing of steel would be change at all whether of not we use some of it in home building. The one beauty of steel and concrete is that neither burns or rots. Other than the primary structural columns and beams of a home built of steel that the framing is of a very light gauge, 22 or 24 guage galvanized steel. The structural members are also lighter than we would use in our refineries and tall buildings, and are either well primed or galvanized. Also, all of these materials are readily available and can be obtained in prepackaged form. Here are some examples. One can find many more steel home packages by simply typing steel homes in google. If you were to read the propaganda that accompanies the examples I gave, he would find some very good arguments for the use of steel over wood, too. Also, one can find more good arguments for and against here, too. Yes, steel manufacturing does use coal and does put carbon dioxide into the atmosphere but I doubt that anyone will argue against steel production our modern society. Just because our society is largely responsible for global warming is no reason to through the baby out with the wash water. Rather we need to use a more common sense approach to how we use our resources. When we use materials that are more reliable and require less maintenance we are also saving energy and reducing pollution.

Hi chtank,

• first of all, concrete is the engineers dream as a construction material. It was first used by the Romans 2,000 years ago and some of the concrete structures still stand.

While the Romans did us concrete to construct things like the Pantheon I doubt they were the first as they were notorious for nicking technology from societies they overran. There is actually some evidence that the Egyptians used a form of concrete to construct sections of their pyramids.

The problem I see is with the way we construct modern houses with light weight frames clad in plasterboard (Drywall, Gyprock etcetera). While they are cheaper than solid brick and other sturdier techniques they do not last anywhere near as long and when you take this into account the are no cheaper.

We are currently living in a house that was constructed from solid brick over 90 years ago that had a timber frame Gyprock clad extension added less than 20 years ago. The newer section now looks very tired and is in serious need of extensive refurbishment while the older section only needs a coat of paint. Another problem is the energy consumption and even though the newer section is insulated to current standards it consumes around an order of magnitude more energy to heat and cool. It is also no where near as good as insulating sounds and you instantly notice the difference the moment you turn on a tap and hear the noise generated by the water flowing through the pipes.

We can however construct dwellings that last many times longer and this is where the use of concrete and steel comes in. With a little bit of creative thinking the energy used producing steel and concrete can be offset by the extended life expectancy and reduced ongoing energy consumption required for heating and cooling.

Personally I have and will never purchase a house that is constructed from a light weight frame that is clad in Gyprock or similar materials. The northern half of Australia lies within the tropics and so is prone to destructive meteorological events like tropical cyclones while pretty much everywhere that is outside the core of the larger cities is prone to bush fires. Add in the occasional flood, killer hail storm and temperatures that can top out above 40° C and you will get the idea. Light weight Gyprock structures offer absolutely no protection whatsoever to the dangers of such events and are likely to suffer severe or catastrophic damage.

Interesting thoughts Masu.

If you work in the building industry in various places around the country, you'll probably change your view in some respects. Brick dwellings that I was wiring in Brisbane in the 70s had the roof held down by a bit of hoop iron under the top five courses of bricks. No cyclone bolts were installed and no bond beams either. Standards for construction in the South will not stand up in the cyclone belt. A brick building is merely a stack of bricks with some mud to seperate the bricks, great for thermal mass and fairly good compressive strength but no tensile strength whatever.

The buildings that have stood cyclone after cyclone are the solid timber buildings built when timber was cheap. The inner core of VJs nailed from bearer to top plate have incredible tensile strength and strong resistance to racking as real world testing by cyclone has proven.

Fire, now that is another matter, luckily not such an issue (from the bushfire sense) in the North, due to the operation of the seasons (Summer wet season).

Back to the Biomass. A real concern has to be, if greed and stupidity have destroyed the renewable resource that nature custom designed for construction, how is this grow your own fuel thing going to work again?

Hi Emjay4119,

• A brick building is merely a stack of bricks with some mud to seperate the bricks, great for thermal mass and fairly good compressive strength but no tensile strength whatever.

This is true, but modern mortar, if used correctly, can be just as hard as the bricks and offers far more of a protection to airborne missiles that cause many of the injuries and much of the damage in cyclones, monsoons or hurricanes.

As you said bricks and mortar have fantastic compressive strength wile timber has tensile strength so any engineer worth their salt will use them accordingly. In a timber framed structure much of the timber is subjected to compressive loads and that's not good design practice.

There a whole host of traditional building practices that are accepted because that's the way it has always been done that can be improved on. To me it makes absolutely no sense to construct a brick veneer house that has a timber frame clad in bricks then use timber in a compressive load while no more than a few millimeters you have bricks that are only used as a cladding material and are under no structural load at all.

Many years ago I designed an extension to a house that was owned by friends and to save space I utilized the brick part of the structure to do all the support then lined it with a waterproof membrane and attached timber batons directly to the inner surface of the bricks. The batons were attached every second row of bricks using a nail in nylon fastener that would no allow water to penetrate from the brick to the timber or internal structure. The result was a structure that used the bricks in a compressive mode while the timber batons tied the structure together and gave the brick structure added strength to shearing and tensile loads. It worked well and resulted in an outside wall that was around 50 mm thinner and considerably stronger than the normal brick veneer structure. However, that was around 30 years ago and I have no idea if it would be approved by the current bureaucracy.

My point is, whenever you are building a structure you will end up with a stronger and often more suitable structure if you use the materials you are building the structure where they are most suited rather following on blindly because that's the way it has always been done.

As for building a cyclone, hurricane, tornado, monsoon proof dwelling it's hard to go past reinforced concrete particularly if you use it for the roof and tie the roof to the foundations with the reinforcing material. Windows are also a big problem and I would always recommend the use of safety or at least laminated glass. Safety glass is a problem because it can not be cut to fit, however, if you use a standardized window frame size you can have glaziers hold standard sizes in stock to replace damaged panes. Some of the laminating materials around now can offer incredible protection against flying debris but for the most part it would probably be better to have some sort of shutter system that can easily be deployed to protect the windows during such events. Something else that needs to be engineered for is storm serge and first off I believe anybody that builds a structure on a beach or the sand dunes immediately behind it deserves everything they get. If you try and stop water you will fail and the only solution is to not try and stop it but rather build the structure that avoids it. However, it is possible to build a structure that is elevated and can tolerate storm surges by allowing the water to flow under the structure without offering any sort of impediment to the flow.

It's our job as engineers to use our skills and imagination to develop new and better ways of doing things and that includes building houses.

"As you said bricks and mortar have fantastic compressive strength wile timber has tensile strength so any engineer worth their salt will use them accordingly. In a timber framed structure much of the timber is subjected to compressive loads and that's not good design practice."

No not quite fantastic. Use of brick or concrete to support suspended loads eg earth moving equipment or vehicles is illegal and downright stupid. Timber on the other hand is fine. When used as props to support the roof in an underground mine timber is justifyably acceptable, masonry is ok for seals but unless encased in steel is not suitable for props. Can props however, are terrific as the strengths of Aerated concrete and the steel enclosure are combined to provide a structure that both yields when the roof pressure exceeds its compressive limits and resets to full compressive strength when the load has been revieved by displacement.

Concrete and other masonry is useful in bulk. Timber load bearing sections are thin and light therefore useful and space saving. Brickwork cannot handle ground settling without cracking which is why brick veneer is preferred. When the brick work fails the timber still supports the structure. The recent drought broke a lot of brickwork to the point of collapse.

With the extra foundations in place to support it brickwork can be good for thermal mass and low maintenance. Unfortunately face brick is now out of fashion with some of those who just had to have it a few years ago. The current fashion is to chop off the sills and smear it with pretender render to make a Mc Mansion clone. What will happen with the next fashion change? Stick on brick shaped tiles? They already exist, complete with a steel support frame.

The Mc Mansions are not only dead boring, but are already coming apart at the corners and joins because they are fibro over radiata pine and the pretender render is supposed to be reinforced with fibreglass mesh. Many examples don't seem to have enough thickness to hold the mesh. This is one construction technique that would have been better not imported. The benefits of timber are negated by use of synthetic based renders and of course the pine doesn't anywhere match the hardwood frames of years gone by.

Hi Emjay4119,

• The benefits of timber are negated by use of synthetic based renders and of course the pine doesn't anywhere match the hardwood frames of years gone by.

My wife and I own a double brick house in Adelaide that was constructed in the 1960s that used concrete pier and bean foundations rather than the usual concrete slab. We have owned it for 20 years now and have had no problems with foundations moving, settling or cracking even with the current problems with drought.

The floor in this house if pine over hardwood beams and as is common with floors like this there was a board that would creak when you walked on it. I located the offending board and the point it had become loose and decided to fix the problem with the addition of additional fixings as follows:

• First off I use the standard nails used to fix floor boards to beams but after several of these bent I decided something heavier was required.
• I then went to a nail that was thicker but it too had the same problem.
• Not being one that concedes defeat easily I decided the use of a masonry nail would overcome the bending problem. It did but you could not drive the nail far enough into the hardwood beam to be useful.
• Ok, I now resorted to drilling a hole in the hardwood beam to make it easier to drive the masonry nail in but even a hole that was slightly small than the nail would cause the nail to bind and not go in.
• Ok, time for a screw. I drilled the appropriately sized holes and inserted a screw but before the screw was fully home it broke.
• Now I am getting peeved with it so I decided the only solution was to go to metalworking techniques and use a tap. I got a 6.5 mm tap and the appropriately sized drill bits and after drilling the holes started taping the hole in the beam. Guess what? After a couple of turns the bloody tap broke off in the darn beam.

Now I had a pile of bent nails, a drill and tap broken off in the floor and a floor board that still creaked. At this point I thought it would probably be easier to move house than continue but decided that we would just have to live with the creaking floor board.

I have no idea what sort of wood they used for the floor beams but it was certainly the hardest wood I have ever come across.

While the production of concrete consumes massive amounts of energy and produces a lot of pollution I still believe it is a building material that has great potential and could easily be used in far more situations than it currently is. Back in the late 1970s I worked installing control systems in several of the large high rise buildings in Sydney. There were two constructions methods used in these building, the usual steel frame reinforced concrete and a stressed concrete system. The stress concrete system is worth looking at in detail as it has a lot of advantages and is starting to be used more frequently, particularly after the attacks on the World Trade Centre towers. The easiest way to describe it is to go through the construction steps:

• The first stage is to construct the core of the building out of reinforced concrete that contains all the lift shafts, fire stairs and utility riser shafts.
• As the central core is constructed a series of columns is constructed at the other most distant extremities of the building.
• At the level each floor is to be constructed the outer columns are linked with concrete beams that tie the columns together in an outer ring of polygon.
• The formwork for the floor is now installed and what resembles a spiders web is constructed from steel cables that link the core of the building to the beams that link each of the columns.
• These cables are then tensioned and the concrete is poured over them to completely encase all the steel reinforcing.
• Once the concrete is cured the formwork is dismantled and the process repeated on the next floor.

There are a couple of minor variations to the principal but the end result is a reduction in the mean thickness of the slab from around 300 mm to about 50 mm and is free of internal columns. You also end up with a slab that is incredibly strong because the tension in the internal cables places the concrete under compressive loads and the result is a structure where all the concrete is under compression.

There are also a myriad of composite materials that could easily be used in the construction industry to create buildings that are not only easier to construct but considerably stronger and more energy efficient.

The problem is the building industry had incredible inertia and is not accustomed to radical and lateral thinking. If you design a structure that utilized fundamentally different and innovative materials and engineering concepts you will not only have trouble finding somebody to construct it but are likely to have one torturous time getting it improved by the local planning authority.

While the building industry is one of the worst at being reticent to accept change they are not on their own and it is always difficult to changed entrenched ways of thinking. None the less, if we are to adapt our ways and reduce the damage we are doing to the planet we are all totally dependant on we are going to have to radically overhaul the way we think and do things.

Well said, masu:
"While the building industry is one of the worst at being reticent to accept change they are not on their own and it is always difficult to changed entrenched ways of thinking. None the less, if we are to adapt our ways and reduce the damage we are doing to the planet we are all totally dependant on we are going to have to radically overhaul the way we think and do things."

Back in the '50's, while I was still in college, a contractor built a house near my home that was 100% prefabricated double walled (~50 mm open space between two walls) concrete. The roof was also reinforced concrete. This house was innovative to say the least, yet the idea never caught on and the three demo houses were the only concrete homes built in the entire neighborhood. The houses still stand after all these years and none have had to be treated for termites and none have ever burned.

Concrete is also an outstanding heat sink and heat transfer through concrete is slow to say the least. As for new composite materials, consider this, NASA and the aircraft industry are relying heavily on carbon fiber composites. Also, in some cases, our industrial structures are have been using fiberglass structural members for quite some time. I happen to have an electrician's ladder which is made with fiberglass rails with aluminum treads. This ladder is quite sturdy and has outlasted all of the wooden ladders I have owned. If you wish to look at using composites in your structures, simply type 'composite structural material' into google to start your search. I have found all sorts of composite structural material this way, including carbon fiber mats and resin for making my own custom shapes. Note, too, that heat transfer through composites is far slower than through steel or glass, and in some cases, concrete and wood, too.

Masu,

Buy a nail gun, but take care that vengeful hardwood can still fight back. I was drilling some Bluegum blanks last night to make some pens and it decided to be a challenge, you know binding the bit and all that. The "soft" hardwoods like Mackay Cedar and Silky Oak were a dream.

When I was involved in highrise as an apprentice (and how I hated it), I worked on both reinforced concrete and steel beam buildings. The steel beam models have since become a problem due to asbestos required to shield the beams from heat (for instance RBH block 7). The reinforced concrete buildings were cast insutu but seldom tensioned, post tensioning is certainly a way to reduce mass, cost etc as it makes use of concrete's greatest asset compressive strength. Bridges and wharves etc (even railway sleepers) that are prefabricated have utilised this method for years. Even in the 70s steel beam construction was the exception in Brisbane.

We need concrete, we need steel, but my argument remains that replacing timber in construction with manufactured material is not going to reduce CO2 emissions. Mismanagement for instant profit is the big issue and remains the central issue for biomass as well. Refer to Borneo again, tearing the scrub (old fashioned politically incorrect word for "tropical rainforest" down to plant oil palms does not seem like a positive move. Yet and yet the Malays market the oil so produced as "Ecofriendly".

Hi

• Buy a nail gun, but take care that vengeful hardwood can still fight back.

I gave up, conceded defeat and moved house. No, we have since moved house and while we still own the house in question we now rent it and if the current tenants don't like the creaking they can solve the problem themselves.

I havn't been to Brisbane in over 20 years and couldn't find my way around it in a fit but one of the buildings I worked on that employed the techniques I was describing was the MLC center in Sydney. Originally it was meant to have 86 levels above the main lobby and 7 below but the height restrictions imposed by the Sydney council limited the tower section to 68 levels. However there were two other building built on very much the same design and one of them was in Brisbane. I had a look on Google Earth and as far as I can see the building I have marked with the red arrow looks like it is the Brisbane version.

It's easy to tell as there are no internal columns and if they did the same as in Sydney where they didn't install a false ceiling in the main lift lobby, you can see the spiders web structure I was talking about on the underside of the slab for the level above.

There were several other buildings that are round and were built using a slightly modified construction method but it was very successful and you can use it to construct sky scrapers that are much higher than any of the ones built so far.

The formwork for pouring the concrete in was a series of three gigantic fiberglass moulds that could be broken up into small pieces that could be handled by one person. If I remember correctly they had three sets, one being dismantled, one being assembled and the third either being poured into or curing the concrete. I was told they used the same set of moulds for all three buildings but I have never been able to confirm that.

When we did the Wooloongabba Telephone exchange, it was done with waffle pan moulds made of plastic nailed to the form ply. What a nightmare. Every conduit had to be bent accurately around the waffle pans and secured to assure coverage. Every cable run became a Zig Zag. Being a Commonwealth Govt job PVC conduit was banned, only screwed steel conduit was allowed. Of course no pre pour wiring was accepted so when the concretors and their vibrators had had their way with the threads there were plenty of conduit runs that wouldn't swollow the snake. This left surface running as the only option. There was no ceiling so the the steel (of course) conduit had to accurately and neatly follow the centre of the waffle ribs (max 100mm wide). 40mpa concrete and a vibratory drill off a 10foot step ladder (Govt job remember, no aluminium ladders and fibre glass ones weren't yet around) in Brisbanes Westerlies on say the 8th floor with one bit of pipe for a safety rail. Oh what joy, oh what fun. Thankfully Mr Hilti released his TE17 Rotary Hammer during this time so after burning out about the first 250 Rawlplug masonry drills, I was finally supplied with one. It was still a terrible job but at least it was actually feasible with help from Mr Hilti.

We didn't know about carbon footprints in those days, but the footprint of the worn out drill bits alone would have kicked 2 men to the moon.

Even though the CO2 story wasn't running then, the "grow your own fuel thing" was going, especially in Brazil and for a while in NQ as the first Oil Shock was still hanging about.

On the building I worked on it wasn't that bad as in most areas there was a false ceiling that could be used to hide everything and all the plumbing was confined to the central core structure. However you were not aloud to drill holes in the slab because hitting one of those cables that were under considerable tension could really ruin your day. When the slabs were poured they had penetrations for all the cabling and utilities and each floor had a small control and electricity distribution room that were linked along the entire length of the building. Once an area was completed the penetrations were sealed.

When the slabs were poured that had hooks imbedded in it that could be used to anchor things like the sprinklers and air conditioning ducts but the lighter stuff was all held up with clips that were glued to the underside of the slab. While the structure of the building and internal core with all its gear were designed to last for around 100 years the floor fittings were designed to be replaced every decade or so.

One of the things they didn't allow for was the installation of large computer systems and the power and cooling they required. Some years later when I was working for a company that produced super mini computers I was involved in installing a system in the building. I had no end of problems with things like it overheating, power fluctuations, earthing etcetera.

Since mini computers have sort of become extinct that sort of problem has mostly gone away and the later buildings that I have seen built along the same lines, have been saturated with CAT-5 cabling. However, with any building like this you are always going to have problems with allowing for new technology, but any engineer worth their salt will be able to allow for this and construct the building accordingly.

Note that I said engineer and not architect. From what I have seen most architects have no idea how to build the things they dream up and it's the engineers who figure out how to build it and make it useable.

"Note that I said engineer and not architect. From what I have seen most architects have no idea how to build the things they dream up and it's the engineers who figure out how to build it and make it usable."

AMEN!

Oh yeah. Archichokes dream it up Gingerbeers plan it and the tradesmen have to make it work.

Hello gentlemen!

My question (and suspicion) is: Isn't a hydrogen infrastructure just another monopoly waiting to happen? And why not FINALLY make electric cars what they should be: Fun to drive, economical, reliable, and not controlled by foriegn countries. I have seen data suggesting hydrogen cell cars will never be as efficient as a pure electric car. (with improved batteries) Your thoughts please!

Thanks, Bryan

Of course it is.

Why else would the Bush/Haliburton whitehouse be pushing for it!

As Masu [& others] have pointed out the energy density for hydrogen, just ain't that good.

There are many solutions, electric transportation all ready has infrastructure in place & would require the least amount of r&d to implement.

The only thing required is the political will to stop subsidizing big oil & incentivize the auto makers to use the r&d we already paid for.

Thanks for the response! I will look the into MASU referance. I could "GOOGLE" different topics, but you know how much crap there is to sort through. I would greatly appreciate all the scientific data, studies, and the names of reputable scientific organizations, that can show the TRUTH (good & bad) regarding the future of personal vehicle transportation. Public transportation is already a step in the right direction for many people...but not everybody. That's why I want to educate my state representatives about the best policies to follow, to avoid additional corporate greed, and the most "green" technologies.

Thanks!!!!

"I would greatly appreciate all the scientific data, studies, and the names of reputable scientific organizations, that can show the TRUTH (good & bad) regarding the future of personal vehicle transportation."

MASU and others have been publishing links time and again to fill this request for information. To start with, let's not forget that the Government of the United States has many dedicated and hard working employee. With that in mind, let's start the Department of Energy (DoE), the Environmental Protection Agency (EPA), and NASA. I have taken the trouble to link to the pertinent sites to fill your request for data, doing so using Google. Now there are some other sites that describe equipment that is currently being manufactured, some is just now coming on the market and some have been on the market for several years. Let's start with solar and wind power used to generate hydrogen by Distributed Energy Systems. Next is Fuel Gasifiers that Siemens has had successfully in operation for 30 years producing a variety of gas and liquid fuels in Germany. While you are on the Siemens web site, you might find a number of other items you might ask you State Representatives to look into. Please understand that the great State of Texas is a leader in green energy and has more wind power plants in operation than any other state in the Union. One additional link is to an up and coming small manufacturing company that produces Solid Oxides Fuel Cells (SOFC), http://www.acumentrics.com/products-power-generators.htm (sorry, link no longer available) in the 3 to 5 KW range, ideal for home owners and for export to developing nations.

We can and, in time, will move to these alternate and renewable sources of energy. We have heard detractors who point to the heat output from SOFC as being too too for the automobile, but believe me, burning gasoline in an internal combustion engine is hotter than that produced my the SOFC and that heat can be put to work in a combined cycle co-generation unit. Look at what Siemens suggests.

I was reading just today in "Science News" that Wall Street is shying away from the hydrogen only fuels cells and moving toward the multi-fueled fuel cell. The SOFC does work on most any gas or liquid fuel. And as far as teh contamination of the fuel cell by sulfur and other like pollutants, you will note that the filters need be service only once a year.

I am sorry you do not want to do the little bit of work it takes to do a Google search, but if you had the strength to do so, you would find hundreds of site with lots of good information on these subjects.

Thank you chtank! Please understand that I'm not afraid of surfing google! I do it all the time. I just asked for ACTIVELY concerned individuals like yourself, for the most CREDIBLE information available! Thanks! I'm trying to find data that is concise and easily understood by the average American, and their representatives. I also want to compile rebuttal data; for the occasional hydrogen-zealot. Thanks again!

PS I've also found some good authors on youtube...really! I'm going to try AMAZON too.

Thanks again.

Chtank,

I didn't realise you had an SOFC. Please keep us posted. At one stage I looked at what MTU were doing in that field, they claim great efficiency due to high quality heat that is utilised in their application, power generation for hospitals etc.

To look around Texas at the progress in alternative energy would be a good thing. I hope to do it before too long. Next week I'll get a look at parts of Illinois and hopefully a bit of Wisconson, I'm also hoping to meet at least another member of CR4

Actually, Emjay, I do not HAVE a SOFC. You see, I am 74 years of age and living on social security. All of my savings have been used up to aid my wife, who has had knee replacement surgery and is due for foot surgery and the other knee to be replace, except her age and health may prevent the surgeries. I, also, have a few health issues and is the reason for my retirement in 1998.

I had planned to continue working into my 70's. Thus, to keep myself mentally active, I have been using the computer to do some personal projects that I had dreamed of since I was a teenager. One of the projects was to replace fossil fuels bio-mass fuels. Yes, I did consider this way back in the 50's and 60's. Because I was a chemistry/physics major and because father had the privilege to work with Dr. Van Allen doing research on radiation and the effects of radiation, I had the opportunity to learn about the early research being done in the effects of our uses of both nuclear and fossil fuels. I regret that my GI Bill ran out before I was able to complete my degree, but my experiences in engineering with the US Army Corps of Engineers, in private industry with heat exchanger, refinery, power plant, and chemical plant design has been an eduction in itself. My continued interest and later research in the physical sciences has lead me to look into Nanotechnology, photovoltarics, power generation, and alternate energy sources. In the power generation area, I examined the solar cell, wind turbine, and fuel cell for its potential an found serious problems will all except one schema as a replacement for dependence on fossil fuels. This is the schema I am currently promoting, i.e.:

• The use of solar cells and wind turbines to produce hydrogen to "enrich" natural gas in the network of pipelines world wide.
• The use of biomass to produce syn-gas to be included in the natural gas pipeline stream(s) and to produce alcohols and other additives to be used to "enrich, compliment and supplement" liquid fuel(s). I see this as being the only practical means to "ween" ourselves away from the dependence upon fossil fuels without disrupting the economy. It is, also, a means to solve the current problems of waste management.

• The fuel cell is a very efficient battery. The Lithium Ion battery has a very high energy density. Other electrical storage devices are being developed and improved daily. However, all have some real or perceived problems which may or may not cause a serious delay in their acceptance and deployment. As I researched and sorted through all of the options, I settled on the SOFC as the one device which can immediately fill our energy needs in both the industrial and private areas. It is the ruggedness and the multi-fuel capabilities of the SOFC plus the outstanding efficiency of the cell (55% without heat recovery, 90% with heat recovery) that lead me to this conclusion. As a bonus, too, it seems the SOFC is easily the least expensive to manufacture, maintain and operate, and is coming on the market NOW.

Thus, the schema is to use all solar cells and wind turbines to produce hydrogen, use biomass gasification and liquidizing to feed SOFC's to produce electric power. TGhe access liquids can then be used to enrich fossil liquids. Note, too, that the SOFC can be used in transportation, the heat can be recovered an and used for more power generation and the heat is not any greater than that produced in the exhaust of internal combustion engines or in turbine engines.

This is my story, I hope it can be of benefit to you and can be a benefit to all of humanity.

Hi chtank! Here's my economic/technology dilemma: Did we need to "ween" ourselves from the horse and buggy? No. Early electric and gasoline automobiles became the logical choice for the majority of American families. Pure-Electric cars are SOOOO much more simple to design and repair, and hybrids are nice for their range capability and "weening" factor. So why should we develope and promote complex technologies and infrastructures for fuel enrichment? I'm not an expert on sofc or other cell technologies, but they seem unneccessarily complex , and vunerable to corporate greed. My gut feeling is that electric cars and their batteries can easily be refined, and when long range travel is needed...hybrids. (Hybrids burning clean, efficient fuels) Thanks for you thoughts and perspectives!

Too bad you are too young to remember the horse and buggy days. The roads were not paved and were filled with horse shit. Of course, here in Texas we still have a lot of that Texas fertilizer so we are very familiar with it smell.

Keep in mind, captbryan, a fuel cell is a battery. It just so happens that the fuel cell battery is fuel able and will, like an internal combustion engine, run so long as it is fueled. It just so happens that the fuel cell, especially the SOFC, is at least twice as fuel efficient as an internal combustion engine, far more simple, has no moving parts, requires no lubrication, and needs to be serviced about once a year. Now, add that to your simple to design and repair electric car and smoke it. I suggest, before you knock the idea of fuel cells that you examine the links provided and learn a little bit about it. In this way, your criticism becomes far more creditable. This is a very long and much used thread that is originated by a very knowledgeable engineer. For the most part, the replies to his original post are also by very creditable engineers and scientists.

Thanks chtank! I would like to educate myself regarding the complete facts of cell technology. It sounds like you know what you are talking about, regarding cells!

But....I still believe than "refueling" at ANY type of cell, at a corporate owned, brand-name "filling station", is just switching monopolies. My preferance is to refuel at home, via AC outlet. I HATE being a puppet to oil companies, (with record-breaking profits) and foreign countries. I trust the electric companies more. (but not absolutely)

High-tech Batteries: I'm more inclined to trust wal-mart, napa, bumper-to-bumper, and other automotive chains to drive down the cost of high-tech-batteries. I don't trust Chevy, Ford, etc...to develope an INEXPENSIVE/STANDARDIZED "cell" pod/case/whatever. I don't trust the auto companies to do the "right thing". I only trust them to do the "profitable thing". That's not paranoia, that's history.

If you can recommend cell websites or agencies, I'm willing to be convinced, and I will gladly check them out. Thanks, and best wishes , Bryan

Start your own fuel company, all it takes is a little money and some engineering know how, the best place to start is by building yourself a still and distilling alcohol. But then you can gasify you trash and save lots of money plus help do away with landfills. Finally, you can use this fuel in fuel cells to make your own electric power, that switch you want to throw. Don't for get wind power and solar panels, they too, take a little money and some engineering know how. I do talk about all of this in "My Earthbound Space Station" and in my blog, "A Dinosaur's Thinktank". I think, too, that MASU gives some links that you can sue to build your own biomass refineries. I would also suggest you invest in Mother Earth News as well. They are filled with home remedies to "Corporate World". But keep in mind, Corporate World is filled with people just like you who try to make profit from their hard work. Granted, there are a few who want to screw the world, but in time those Enrons and Exxons of the world get their just dessert.

As an addendum to my last reply; while looking at me Fuel Cell journal, I noted that On Shetland Island, if my memory holds it right (I deleted the article) and in Germany, pilot plants are being constructed to power individual homes using fuel cells. The article did not go into detail, however, it appeared that the schema I have suggested is being used. I am sorry I did not retain the article for you, but perhaps you can do a search and find a reference to the article.

I get:

4.35 x 10²⁰ [joules/year] * 1/365.25 [years/day]

Crop_Area= ^{____________________________________________________________________________}

1 [kW/m²] * [1000 W/kW] * 1 [joule/W-sec] * 3600 [sec/hr] * [12 hr/day]

Crop_Area= 2.76 x 10¹⁰ [m²]

Wikipedia, under "Energy Crop" has a list in terms of mass or volume of fuels per acre, that should be easily turned into a set of efficiencies, if I didn't need to hit the sack now.

Algae looks far and away the best, and the solar collection efficiencies of the rest must, therefore, be pretty poor.

Doing the calculation again I get the same final figure as you. I did that calculation three times and I have ho idea how I ended up with the figure I did. Nonetheless, that's why I try and put in as much of the work in my posts, that way if there is a mistake it doesn't get used in further calculations.

Ok if we now work on the new figure and add a little for growth we end up with needing around 30 x 10⁹ m²

As some have noted, algae seem to be a very promising possibility. It can result in higher energy density per acre than any other crop and do not have the food supply impact of corn, etc.

There is extensive work going on to use various algae strains that are composed of 50% or more lipids that can be easily converted to biodiesel. Once oils are extracted, the remains can be used as feedstock for biomass reactors, fertilizer, or some other use. Algae have a much higher yield per acre than any other crop, because of their simplicity and resulting efficiency of solar energy conversion. Some strains can even be induced to produce hydrogen rather than oxygen as a byproduct of their metabolism.

Wikipedia has decent summaries of what's being looked at, just look up algaeculture or biodiesel.

Back in the 1950's, when I was in college, I wrote a research paper for English Composition titled "Food from the Sea". Most of my material was obtained from the University of Texas and a study which they had conducted. The paper was a description of the harvesting the algae an plankton that grew in the first 40 feet of the ocean. This included seaweed. One of the conclusions was that a one mile wide strip of ocean from the west coast of California to Hawaii of seaweed can supply all the energy needs of the entire world for years to come. It also described algae farms that could be harvested which could be made to taste like chicken, steak, or any other human food stuff by varying the nutrients given to the algae during its growth cycle. It has been over 50 years since I did any research in this area and all my papers and note have been lost. I bet, however, that one can search the achieves of the University of Texas and find some information. Also, I have no idea of how much research on teh subject has been done since the '50's. What I do know is that algae can be grown to force the discharge of hydrogen rather than oxygen and that it can aslo be grown to produce an abundance of sugars that can be easily fermented into ethyl alcohol. As for a food stuff, I cannot be sure of its value but I do know that algae can be fed carbon dioxide to stimulate its growth.