Posted by: joachim in Renewable Energy,Solar on July 29th, 2011


Geothermal Heating Systems for Homes

Domestic Geothermal heating systems can be a great way to heat your home, replace a furnace, and are labeled as money savers. Question is, are they worth the hype? Here’s a quick view first of how they operate.  Starting at depths of between 6 and 10 metres, the temperature of the earth is no longer influenced by variations in surface temperature, and stays relatively constant at around 8 to 10 C. So the underlying principle of geothermal heating and cooling is to use that consistent interior earth temperature to balance our wildly varying American & Canadian surface temperatures.

With the use of heat pumps, geothermal heating and cooling systems extract heat energy and transfer it into buildings, saving you approximately 50 to 60% on heating and cooling costs, depending on the fuel to which you are comparing.

In summer months, geothermal cooling functions in a similar way to standard air conditioning, only heat is not simply ejected into the outside air, but rather deposited deep in the ground for future use. The result is guilt-free air conditioning because you are actually using the heat extracted in summer months to warm the earth deep below, heat which will increase the efficiency of your system in winter months.

Geothermal home heating systems:

Vertical closed-loop systems have a sealed U-shaped pipe of high density polyethylene that carries a heat transfer fluid (usually a water / methanol mix) in a continuously circulating loop allowing an exchange of heat by conduction. As the liquid returns to the surface, either heated or cooled depending on the season, the additional or reduced amount of heat in the water is used to condition your home. The required depth for this system is generally 300 feet or more, and you pay for it by the foot. Through the nose, but by the foot.

Geothermal vertical loop system © Alexandre Gilbert

Horizontal closed-loop systems function in the same manner as vertical systems, except that pipes are run back and forth 6 to 10 feet underground. Installation involves excavating trenches (at least 300 feet of them), rather than digging a well. You can visit for any electric related installation.

Horizontal systems can be cheaper to install but require a significant amount of space, and it does some pretty intense damage to any ecosystems that lay in its intended path. For a given length of pipe, horizontal loop systems are a bit less efficient than vertical loop systems, as they can be more easily affected by surface temperatures. The other downside is that if or when there’s a leak in the circuit, with a horizontal mat or grid style system the whole garden area has to be dug up again in search of a tiny leak that is losing the system pressure.

Geothermal horizontal loop system © Alexandre Gilbert

Open-loop systems use ground water pumped directly from a supply well (75 to 100 feet deep) in order to draw and inject heat. Water is pumped out of the first well, and after the heat exchange is carried out, it gets injected into the second well.

Geothermal open loop system © Alexandre Gilbert

Open-loop systems have a very high thermal efficiency and installation can be up to 50% less expensive than vertical closed loop systems. However, conditions necessary for the proper function of these systems are rarely found in urban areas, as they require an abundant source of ground water.

Will geothermal heating save me money?

That truly depends on the size of a project. No geothermal system is cheap to install, and because it offers only a reduction in consumption, the return on investment is really only viable for larger buildings. For this reason geothermal is more suited to commercial or multi-unit residential projects of substantial size. On the other hand if you are willing to save money by reducing energy cost make sure to get proper maintenance from Coolbest air con servicing for your cooling and heating devices.

A home would have to be quite large, and somewhat poorly-insulated to actually make it pay for itself in a reasonable time frame. The main goal of attic insulation4us in the house is to keep the rooms below warm in winter and cool in summer. In many cases, particularly with moderately-sized new homes being built, that large of a financial investment towards energy efficiency could offer much greater returns if put towards heat retention instead - better windows, additional insulation, better tapes and membranes for air sealing, etc.

Ball park pricing: A geothermal system for an averaged size home (2000 sq. ft.) would easily cost you $30,000 to have installed, and that is in exchange for a monthly saving of about 50% on your heating bill. So payback for the average single family home is simply too far away to make this a financially competitive option with all but the highest consuming homes.

That same investment of $25,000 (or perhaps less) in a better thermal envelope would likely reduce your heating bills easily by 70 or 80%, perhaps more. Geothermal energy is an excellent global technology, but for single family homes you will get far more bang for your buck if you put that money into insulation instead.

With so many places on earth where photovoltaic power plants could be built, it is not always immediately obvious where the best opportunities are for investors or project developers. For instance, lack of sunshine in one country may be compensated for by a high feed-in tariff. For a first-look, crude comparison of two opportunities, projects may be scored on 5 dimensions: Irradiation, tariff, system performance, capital expenditure and a general assessment of political stability & local knowledge of the team.

If shown as an area in a graph, the ideal project has an area that is large and balanced around the center. If the area is mostly in the top half of the diagram, the project has great potential revenues, but may never be built because of costs and political risks. On the other hand, if the area is mostly in the bottom half of the diagram, the project may be safe to build, but won’t generate a lot of cash.

In the graph below, we are comparing two ficticious projects in northern Germany and Tunisia. Furthermore, the modules in Tunisia are mounted on a tracking device, resulting in higher system performance because the tracker allows the system to catch more of the available irradiation. Also, annual irradiation in Tunisia is twice as high as in Germany. On the cost side, however, the tracking devices adds to the price. Finally, the success of a project and its prospects for investment very much depend on country-specific aspects such as political stability of the law governing renewable energy, ease of doing business and getting permits as well as local knowledge. Here, a project in Germany would definitely score much higher than in Tunisia.

The areas of both projects in the graph are of similar size – they both have merits. However, they are also both slightly imbalanced: Irradiation in Hamburg may be too low while political risks may jeopardize the project in Tunisia.

Please try out our interactive tool with more details.

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2 Responses to “Geothermal Heating Systems and Solar PV Projects”

  1. Pedro Leão says:

    Good afternoon,

    First of all, congratulations on your web site. It looks quite professional and interesting to read.

    Regarding your “project comparison tool”, I totally agree with the methodology but considering my own experience with PV systems, I consider that it misses the capture of both some very important issues that also count on comparing 2 different projects, namely:

    - The scale of the projects that on solar could mean economies of scale, which can increase the value per MWp installed;

    - The EPC company that installed the plant (Track-record, quality standards, warranties, etc.). Also for O&M services supplier.

    - The equipment brands installed (panels, inverters, trackers, etc.), since they could mean a lot in terms of smooth operation versus problematic operation thus resulting on lower prodution rates.

    - The contracted PR and O&M Service Levels in case of failure, since this also could mean value at the end of the year.

    In my oppinion, all these items are strong enough to be considered as additional comparison dimensions.

    Kind regards,
    Pedro Leão

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