Geo-sensible Alternative to Traditional HVAC

I think the abandonment issue would result in some rather problematic issues depending upon where you use a geothermal heat pump system.

Us northerners have naturally colder soil temperatures that can go down for hundreds of feet with only a few degree temperature change in that distance. Basically pulling heat out of cold ground takes a fair amount of energy and that will greatly reduce the efficiency in terms of recoverable heat. However that cold ground does give us considerable advantages when using it as a heat sink for summer cooling applications.

The reverse of this can also become a limiting factor in locations that have very warm soil conditions from naturally occurring geo thermal energy. They may have excellent heating efficiency but then poor cooling efficiency. If your in the northern or far southern parts of the world you need more heat for less cost but yet your stuck with cold soils that just don't have as much efficiently recoverable energy available. If your more equatorial located you could have soils that may prove to not be able to absorb the annual air conditioning heat loads being pumped into them resulting in a less efficient cooling capacity of a system or the need for a very large heat sink area.

One large issue I have seen that greatly affects the cost outlay of a geo thermal system is the well drilling or trenching required to set up the heat sink/source end of the system.

Greed and lack of competition in the installation industry is a big factor on the cost outlay for a system at this time. Contractors charge premium prices for basic trenching services and the same with the well drillers. I have several well drilling companies that charge up around $10000 for a 200 foot deep thermal well based on what diameter is needed. Thats about 10 times what the materials cost and they unusually can do a 200 foot well in one day. They have trucks and rigs that are ancient that have where paid off decades ago! To further add to the cost outlay several deep wells may be needed just for one standard sized home if its in a colder climate or in a location with warmer than average soils!

In some applications geothermal can be very efficient and practical but yet in others it may have some serious limitations. And as long as greed and lack of competition are around non of it will come at what could be a cost outlay that would truly push it into more applications and common usage.

Many years ago I read an article in one of my trade journals about the long term efficiencies of different closed loop systems. In that article they said that a long term study of well type and horizontal type closed loops was done somewhere over in Scandinavia. During the first couple or three years the vertical loops had a distinct energy advantage, however, because they were taking out more energy than they put back in on an annual basis, the vertical loops got colder over time. Thier reasoning was that on the horizontal loops the sun's energy only had to go down through 8 to 10 feet of earth to replenish the heat removed during the previous winter, whereas the vertical loops had a lot of thermal mass around them, but it was so much deeper, on average that it was taking the sun's energy longer to penetrate to the middle and especially deepest parts of the loops. So over the long term the horizontal loops are the way to go. They are also more servicable in case of a leak. On the subject of leaks, the manufacturers of the plastic pipes almost exclusively used for these systems have developed a fusion welding system where the end of the pipe and the end of the fitting are both heated to the point that they are soft enough to melt together and the joint is actually stronger than the surrounding pipe, when done right. Also a system, properly done by a professional, will be pressure tested once all the welds are done to verify that both the pipes and welds are leak-free. This may be done with compressed air to begin with, but usually is followed up with a water and,or anti freeze mix to better find any leaks before burial. Almost always these piping systems carry a 25 year or longer warranty these days.

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>>>> That being said, the best choice for loop systems is to bury the loop pipes in the mud at the bottom of a lake. (at least 8 to 10 feet deep) This will get you much better conduction of heat to and from the loop and you can get by with fewer feet of loop pipe per ton. It also saves you a ton of money on trenching, thus making it more cost competitive.

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>>>>>> There are some other advantages to a water source heat pump that some people overlook, such as quietness of operation, no outdoor unit to get clogged with cottonwood fuzz and dirt or be damaged acidently by the kids' footballs or other toys, long equipment life, low energy consumption, and when coupled with a 4" pleated or media air filter, lowest maintenance cost that I've seen. I hope that these comments are of some help to some of you and/or your customers.

Another problem is the development of leaks in the buried piping (poor joints, corrosion, soil shifting, etc.) My brother had a ground-coupled heat pump which worked great and economically for a while, but sprang one or more underground leaks. Such fluid loss can also contaminate the soil.

I really like what everyone is saying, here is something I would like to add.

First even though it might be a good engineering solution, when we present it to a customer. The first thing he wants to know is the cost. If we can show the customer that it does have a reasonable payback (within three to five years). We might be able to convince an environmentally friendly owner that it is a good idea.

Second, no engineering firm is willing to sell a system unless he is sure it does not come back and kick him in the butt. Geothermal systems have been around at least 25 - 30 years so most of the technology is solid at this time. The problem is in the installation. You have to find contractors who know how to install the system correctly and will not cut corners. Thus the lowest bidder may not be the one you want to install on this project unless you are using a manufacturer recommended contractor from a select bid list.

Third, all newer installation of energy efficient equipment both mechanical and electrical require maintenance. Most companies fall into a trap believing they can save money by not maintaining there systems. This usually comes from the accounting department who do not see a return on there money by investing in trained, skilled personnel.

In all it breaks down to money, cost of installation, and cost of maintaining. Does it pay itself back? How much will it cost if the system is a failure?

Now I know there are some who will tell me about saving the planet and business should share risk in the research of a better life, and I actually agree with you. But I would like to know what ever one else is risking? The leadership of companies are not only answering to stockholders. They are risking the entire companies ability to do business in a competitive world, and the livelihood of everyone of there employees. Not to mention the effect it will have on all of its vendors.

"It's hard to get veteran business owners to try new technology." It may not be the new technology that holds them back but rather their "bottom line". Maybe a pole of some of these veteran business owners to ask what kind of ROI they would like to see for upgrading their facilities, would give you an idea of the price point you need to look for...then find the technology that fits that.

The biggest problem I've found is the high initial cost and the lack of good estimates on savings. The cost of drilling a well (or several wells) is very high. This quickly becomes a limiting factor in many installations. The rigs are also quite large and expensive. As rigs become smaller and less expensive, I think you'll see a large surge in ground source units. In the mean time you're limited to expensive wells drilled by certified water well drillers ( a very elite group in most states ).

I think it would be too expensive for companies to implement, especially on a competitive basis with other companies. Geo-thermal HVAC is best suited to new construction, but may be cost prohibitive as a retrofit. Any system that depends on a temperature differential to work, will limit it's use to specific areas and will be a "custom" installation. In order for a system to be efficient, the temperature differential must be kept as steady as possible. Wide temperature variations, result in poor performance. I think you will end up substituting one set of faults with a difference new set. In the long run, it will probably boil down to the cost of generating energy as the deciding factor.

do you mean ground-source or geothermal? let's not confuse another term. geothermal involves drilling significantly deeper holes than ground source and is normally only justified at certain favourable locations.