Electricity from Domestic Gas?

Thank you. If the inertia is mine and the friction is with the neighbours, then I could deal with that. The sticking point seems to be the conversion efficiency, though I was already considering adding the generator heat into the central heating system. The reliability problem is solved by having the mains supply as a backup. For noise, I have been surprised at how quiet some of these generators can be, But as for maintenance cost and insurance I have no clue.

Update:

After chatting to a neighbour, formerly the project manager for one of Rolls Royce's jet engines, I find it's been done already, though the idea makes sense only for a larger house. The firm Flow Energy manufactures "boilers that generate electricity" and claims 30,000 customers already.

The premise that this makes better sense with a larger house does make sense to me. Particularly when one considers the grandiose manors of some of the older family homesteads one finds in Great Britain. The co-generation aspect also appeals to me. The co-generation aspect will probably tip the economic advantage point more than many will realize.

The key factor that we've all stumbled with is the very point your reply hinges upon, the economy of scale, A large manor that will need a boiler to run nearly continuously to heat this drafty manor will likely benefit from utilizing this energy pricing differential to produce electricity and heat from gas supply pricing. There may even be apartment complexes with a common boiler heating system that could in a co-op organization benefit from this approach.

The devil is in the details.

Have you dug around the website for the power gen of that device.

The max electrical power you can get is 1kW which will do your lights and maybe a fridge but wont do anything for a kettle, shower, vacuum cleaner etc

The technology looks interesting I wonder how that scroll device generates power in synch with the 50Hz 240V AC (maybe thats where there is up to 200W power loss from the generator)

I am not convinced power gen in the condensing loop is efficient compared with just heat recovery which is what I had in my boiler in my London flat.

For your overall issue I would add that other issues would be

Ensuring that the power is in-synch with the mains - will the power companies even allow you to connect in your gas fired generator. They are obliged to allow people to buy in on various green / co gen measures but a gas fired gen would not come under those headings (IMHO) - lets face it they do not want people to do their own thing cheaper.

Installing a gas generator in a domestic setting is also likely to run foul of planning laws. There are strict laws about thermal units - flues, height separation etc and I would be surprised, unless you own a large estate if you have the separation from neighbours to install such a device.

The council are also likely to take the view that this changes the property to a commercial venture which would be a problem with planning law.

From an engineering perspective I don't think it is a practical option. It sounds as though you are proposing having a generator that is on full range standby - there will be some continuous use - fridge, freezer clocks etc. Then the gen will ramp up as you use various appliances / gadgets. This means that there is likely to be a huge turndown requirement for the gen so its efficiency in most usages is going to be terrible - you will be lucky to get 10% on your tick over rate (because its such a low rate) compared to 25% at optimal usage

This pattern of use is also the one that will cause the greatest wear on the generator so your maintenance costs will be significant.

It would be an idea if you could get a buy in deal with the power company where they 'bought' all your excess power so you could run the gen at a steady rte for 8000 hrs a year

Decreased power reliability, high fuel cost, and high maintenance cost need to be factored into the justification.

Depending on load and hours of use the gas generator engine will most likely require a major overhaul or replacement within 5 years from date of service.

And my vote is response number 1 on this one...

What you are looking at is kwh equivalency from the energy contained (btu's) in natural gas....Anytime you convert one form of energy to another, either chemically or mechanically, there is an efficiency loss associated with that conversion...Just like the electrical energy you are using to drive a motor, the actual work done when converted is the work done less the efficiency loss....heat, part of the energy is always lost to heat....now if you're converting to heat, as in a furnace, then the electric furnace is near 100% efficient, but in the gas furnace part is lost up the exhaust stack, but still using a gas furnace is usually cheaper because the fuel cost is much lower....so it's all about the type of energy you are using for what purpose that gives cheapest results...Even using a free fuel source, such as solar energy, it is a challenge to beat residential electric rates, because of the scale involved....

http://www.kylesconverter.com/energy,-work,-and-heat/cubic-feet-of-natural-gas-to-kilowatt--hours

When you pay for the electricity, you pay for 100% electricity. I believe a good quality industrial natural gas generator is around the 25% efficiency mark (output compared to energy value of fuel). So while natural gas is great for me to heat my house and water, with a 96% efficiency furnace and 75% efficient water heater, unless you can use the waste heat a generator really doesn't make sense.

Thank you. That is a very important detail. important detail

A better idea might be to simply make use of natural gas in all the places it makes sense. Rather than she'll out for a generator, use the money for a high efficiency hvac with condensing gas furnace, a high efficiency gas water heater, gas stove and oven... you could even line your driveway with old gas lights if you really want to burn the stuff. :-)

If you don't care of a problem of the noise .can you let a generator works along the night with a fuel such like the gas i would like to bring your attention to the safety issue while you want to go to sleep (a deep sleep) . briefly the safety factor

Realistically you would probably get about 25% energy conversion efficiency so it would be a wash on the cost comparison aspect but given a well built engine running at a lightly loaded power level it is possible to do a combination of cyclic co gen and heating making for a fairly effective use of your fuel energy while getting a reasonably long engine service life as well.

I have considered doing this with a modified diesel engine that burns used oil hooked up to my systems to co gen electrical generation while dumping the excess engine and exhaust heat into the heating system.

I just have not found a small 15 - 20 HP liquid cooled diesel engine that was any good so far.

I am not really(an) optimist? Are we having a bad hair day maybe from the picture?

I'd tell em to take a hike and make your own

Australia and Germany have produced a silent fuel cell converter for gas to electricity.
The advantage is you use the heat produced to heat water and the conversion ratio is 100%. Its about 2 - 5 kw

Any link for the 100% claim?

Heat into heat!

Nice!

To what use was that again?

Years ago I looked into this company and was quite impressed. It is German and goes by Senertec Dachs They make a unit that if I remember one unit will heat and supply electricity for 3 homes. I always felt that gas should run and engine for heat and electricity instead of just burning it for heat. Something should be free or near free.

Without reading other posts in detail, generation efficiency ~ 25% for a smallish unit is just about the same as the ratio of prices of gas and elec. If you use the waste heat it looks better, but that's only for about 1/2 the year. Also unless you use a lot of elec you probably need more heat in winter, so boiler also needed. You need a heat dump rad for when there is no heat demand. It could be longer than 8 years payoff, by which time it might need replacing!

If it's a question of scale as hinted by others - ie, the bigger the better - for minimum cost and maximum output - then you end up with a gas fired power station - from which the difference in the cost of gas and electric is built into the price you pay for your supplies today.

As a general rule, the selling price is based on the cost of materials, overheads and profit, so working back and downsizing, your materials will cost a lot more, but you might save on overheads if you can engineer the systems and maintain it for free, but compliance costs creep in, because there are rules and regulations about using approved specialist (backed up by certificates demanded by insurance companies) that you might not be able to avoid, so all that left in the way of certain savings by comparison to what you pay the electric supply company is the 'profit' bit set against the payback period.

There are all sorts of reasons for your idea to be a viable proposition for you, but I doubt if the bottom line cost per unit is the driving force.

I have seen many cases of the use of Natural Gas to generate power for industrial customers for a co-generation facility. In downtown Birmingham, Alabama, USA I did frequent work on a building that had been put up by the local gas company and operated many years by generating it's own power using gas turbines. The original plan was sell hot water to adjacent buildings and share power with another building but the electric utility was able to prevent that. The energy cost savings were good, but the cost of labor for skilled operators hurt them and when the building was sold, it was converted over to purchase electricity from the electric utility. Using the waste heat as much as possible is great, it can heat as well as cool if an absorption unit is used as it was in that building. On a smaller scale, quite a few years ago, an Italian company tried to market a combined heating/cooling/generator that ran off gas and was supposedly environmentally friendly (how you do this with an internal combustion engine is beyond my comprehension) I cannot remember the name of the company, but the engine itself was manufactured by Fiat. The company went nowhere. The problem is that the cost to design and build a quality, low cost, high reliability unit would take a large company a lot of investment and to do it on a one-shot would be even worse and have no payback at all. Any small generator commercially available at a reasonable price is designed for back-up or portable use and would not be reliable enough for continuous use.

Looking at other possibilities, for large houses, a microturbine would be a good choice. The one I favor spins at a high rate with only one moving part. The bearings are "air bearings" and the generator is small because of the high frequency produced and they have designs for almost pollution free exhaust and useful heat recovery. I have seen many applications of these around the world. I am not giving the company name 9 (Mr. Google can find it under microturbine (no space)) because more than one company produces them, although one stands out above the rest. My own employer, when I was working, purchased one the of companies but as field engineers we quoted and supplied units from the other company. They work well and are for the most part maintenance free except for the replacement of batteries every few years. Essentially the generator produces a high frequency AC which is rectified to charge a small battery bank and that in turn is inverted to produce AC at a voltage and frequency to match the local power so no equipment needs changing. These are usually applied in large banks and usually make use of some combustible gas that is available cheap, but they run fine on natural gas with the correct settings. The problem is that it is too much power (30 KW is the smallest) for a small house and the owner must have a staff that is capable of the technology because bringing in outside help would be too expensive. One of the neatest installations I have seen is one where a chicken farm piles up waste and covers it with plastic, takes the gases from the top of the pile and treats it to remove solids and moisture and then powers the houses, outbuildings, farm operations, etc with microturbines and have plenty of extra power to charge electric vehicles. Note that these units have totally different settings than units running on natural gas.

for ex., if a 1/2" gas lateral can supply 10 kw generator, an 8" lateral would supply 1MW and you could resell the power at a huge profit. an 8' lateral would let you supply as much power as a nuclear plant (1 GW).

Maybe you have to turn it on its head.

Running a generator all the hours that you may need some electricity is a non-starter, especially as it would mostly be running at a fraction of its rated load and thus inefficiently. So think of the generator's 'waste heat' as a heating device to come on at full power when needed and sell the 'surplus' electricity back to the electricity utility as you would with a grid-tied PV system.

That also solves many size/scale problems. As an afterthought, if the generator were dc and you used a regular grid-tied inverter, you could add PV panels to the system which would improve the cost-effectiveness of the installation.

Quote

Running a generator all the hours that you may need some electricity is a non-starter, especially as it would mostly be running at a fraction of its rated load and thus inefficiently. So think of the generator's 'waste heat' as a heating device to come on at full power when needed and sell the 'surplus' electricity back to the electricity utility as you would with a grid-tied PV system.

Some appeal to this, but what about a Sterling external heat engine, powered by both solar and gas heat, with lower quality heat going to heat water and area and the sterling and batteries providing electricity as needed. I like the idea of never being tied to the grid. If something goes wrong with the system, then your charged electric car could power things until the problems is repaired.

Your amount of electric usage will be a factor, and the demand you expect to need. If you use large AMP appliances (oven, A/C) you will need a large generator. For lights and small demand a small one will suffice. If you heat with electric it will be a huge demand. Gas is usually cheaper for heating even though electric is 100% efficient. If you want continuous electric you will need a battery storage and charging system which wastes some power as heat is produced. Then there is the noise and heat from the generator to deal with. Just the fact that few use a gas generator unless absolutely necessary should tell you it is not a favorite if power is available.

TANSTAAFL!

I had an IC Engines course last century. The instructor stated that for the engine fuel energy into the engine, 1/3 was into the shaft energy, 1/3 went up the exhaust stack, and 1/3 was into the engine cooling/radiation losses. +/- 10%.

I don't believe there have been any major breakthroughs to vary those estimates to any great degree.

When was that in the 60's there are way more efficient engines today then when most shop teachers were trained back in the day. Just look at some of the of the hi-efficiency imports. And a lot of the newer compacts that have extremely hyper-efficient engines in them. we have come a long way in the last few years for numbers that low in efficiency.

If you are able to use all the waste heat for useful purpose then this alternative is a great idea.

Four kwh of gas would generally produce about 1 kwh of electricity worth 12.31p while giving you 3 kwh of heat energy free!

For this, you might generate electricity that you need 24 X 7 so that the generator is loaded uniformly and electricity generation is efficient.

In winter when there might be a continuous heating need this would be a great idea in your country. Here, in most parts of India, we are sweating it out at over 35c presently.

In fact, in my opinion, just burning gas(or any fuel) for heating purpose only without "extracting" electricity out of it, is criminal waste. Wherever possible, electricity should be generated and only "waste heat" should be utilized for heating purposes.

Ceramic fuel cells that can make electricity from natural gas at 60% efficiency

Yes but the devil is in the detail isn't it

I assume its the ceramic fuel cells company in Oz to which you are referring (seeing as you quote their 60% efficiency) who appear to be about to go bust from the official notice on their website.

I notice in the detail on the product that it only hits 60% if the exhaust gas is cooled to 30C which will condense the water and some CO2 as weak carbonic acid which is an unmentioned effluent. The fuel cell goes via steam reforming so will avoid any SOx, NOx formation but the base unit only generates 1.5kW and weighs 45kg excluding insulation and ancillary equipment. Well for steam reforming you will need a high quality water feed so that means water purification etc

This might become more efficient with stacked units maybe you can get 10 fuel cells into the standard unit and maybe it will only weigh 80kg and the bigger the demand the more efficient the water purification will be in terms of volume processed per area of floor space required.

This looks like a clever technology but I am not sure of its place and the comment that 13000kWh is enough for a home may well be true but this device doesn't supply peak loads and so battery cells are needed for storage - cost, efficiency, space etc

Yes, the devil is certainly in the details here. Notice that the OP in the original question asks for the missing details without providing us with any of the details already considered. You've touched on one of the critical details overlooked by many trying to go completely off of the grid. There is an advantage to providing electric power to a very large field of users instead of one single household. While the average load for the utility is orders of magnitude larger than the single household, the standard deviation in the changing load of a single household is orders of magnitude larger than the utility has to typically deal with. Running an internal combustion engine driven generator or even a more efficient fuel cell all night for the two cooling cycles the refrigerator wants to run and the DVR to record that 2:00 AM program can burn a lot of fuel for very little electric energy. This is why you wisely suggest the addition of some electric power storage system.

The sad story of eight people dead in Maryland should remind everyone that burning fuel inside a residence can always kill. Yes, there are many ways that this can be done safely but it is just as easy to make a mistake and die.

rsalaskar said, "Four kwh of gas would generally produce about 1 kwh of electricity worth 12.31p while giving you 3 kwh of heat energy free!"

how does this make sense economically or scietifically?

It's OK scientifically. 25% efficiency energy in fuel to electric is typical. The other 75% is rejected as heat. Unlikely to make use of all of that heat, there'll be some losses, but I assume it was just a general statement.

A majority of the missing "waste" heat will be in the form of hot, lethal exhaust gasses. This heat is doing the important task of expediting its dilution to prevent the tragedy I cited earlier.

I agree, the waste heat consists of lethal gases including carbon monoxide.

These gases need to be passed through correctly designed heat exchanger to extract heat and the disposed off, safely.

The exhaust heat recovery is common in industry, but at home it needs to be handled with proper care so that occupiers are not exposed to the gases