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Sun Volt Solar

earth, the final frontier

Clean Energy, Clean Environment

We are at a cross roads in human history, we can choose to continue on as we have been, or we can make a change to improve our future and quite possibly the future for several generations to come. We are here to promote energy independence, a better environment, a secure future and a higher return on investment for your hard earned dollar. It is what I believe in, it is why I am in the solar business.

Ground Source Heat Pump; same as a coal stove?

03 Jan 09 | Conservation, Environment, Geothermal

I read a lot of information on a daily basis.  A few months ago, somebody commented that a Ground Source Geothermal Heat Pump is the same as using a coal stove to heat your house.  The notion is that by purchasing and installing a GSHP, a homeowner is only pushing the problem further away (to the electrical generation plant), not actually reducing pollution.

Is that right?  Perhaps a little research is in order.

First, a little background.  A Ground Source Heat Pump (GSHP) uses a refrigeration cycle to move heat either to or from a heat sink which is typically a large coil of PEX pipe burried in the ground.  Wells, ponds and other sources can be used also.  The idea is that using the ground (or other source), which is a constant temperature of around 50 degrees F, a heat pump can be much more efficient than using resistance heating.

GSHPs are rated by a coefficient of performance, known as COP.  This is a comparison of the amount of electricity used by the heat pump vs. electricity used in resistance heating.  Thus a COP of 5 means the heat pump is producing 5 KW of heat for 1 KW of electric used.  The highest COP is about 6, or 600% efficiency compared to electric resistance heating. A COP of 5 is considered very good.

The electrical distribution system in the US is about 31.2% efficient.  Therefore, a head to head comparison of power used vs. heat produced would look something like this:

1 kWh = 3413 BTU

A GSHP using 1 kWh of electric with a COP of 5 produces 17,065 BTU heat.

The electric plant producing the current to run the GSHP burned 10,939 BTU of fuel to produce 1 kWh.  Therefore, a very well designed, well installed GSHP is about 156% efficient when all the energy requirements are considered.

A typical coal stove is about 60-65% efficient, therefore it would require 26,254 BTU to generate 17,065 BTU of usable heat.

Conclusion: A Ground Source Heat Pump ≠ a coal stove.  GSHPs are energy efficient and a good way to heat a home where solar resources are not available.  They are not 500% efficient, as some companies would have you believe, but are greater than 100% efficient if properly designed and installed.

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03 Jan 09 | Conservation, Environment, Geothermal | Comments (10)

Radiant floor heating

12 Nov 07 | Conservation, Environment, Geothermal, Solar Hot Water

Buildings use a lot of energy. Heating, cooling, hot water supply, lighting, and appliances can use lots of electricity, oil, gas, etc. Each BTU that is used requires that something be converted from fuel to energy and by products. The by products in question depend on the type of fuel, but they can be anything from CO2 to NOx, SOx, and mercury to name but a few. As you can see, the more energy efficient our homes become, the less it will cost to energize them and the better off it will be for the environment.

I spoke with somebody on the phone this morning about solar space heating. This is a topic of conversation I had with my brother in law last year at some point. Basically, in this climate, effective solar space heating consists of passive solar design and or radiant floor heating.

Conventional hydronic heating equipment e.g., radiators and base board convectors, requires water temperatures above 140 degrees Fahrenheit (60 C). During the coldest months of the year, December and January, a flat plate collector would not be able to collect enough energy to heat the water to that temperature. Evacuated tube collector may be able to, but the volume of water would not be enough. Most HVAC professionals agree that solar coupled with a radiant floor heating system, where water temperatures only need to be about 85 degrees, works the best.

Radiant floor heating is a really cool idea. These systems work great when a house is built on a concrete slab. Several inches of rigid foam installation is used to insulate the concrete slab from the earth. The heating loops are embedded in the concrete slab and the entire system can be broken up into one room zones. The heating loops use low cost PEX (Cross-linked polyethylene) pipe, which is easy to work with. With a solar system, a small conventionally fired (oil or gas) furnace is required in case there are several days of cloudy weather that prevent the solar collectors from working.

Obviously this type of installation requires a great deal of pre-planing in order to work right. House siting, orientation, solar panel positioning, tilt angles, and heat storage tank options all need to be worked out before the house is built. A new house needs to be designed from the bottom up to accommodate solar radiant floor heating, passive solar design can also be incorporated to enhance the thermal design.

In addition to solar, radiant floor heating works will with ground source geothermal heat pumps. These systems can supply a good deal of heat to larger structures that may be too large to heat with solar collectors alone.

Retro-fitting older houses with radiant floor heating is also possible. Older homes with wood floors require a number of compromises to get the system to work efficiently. In addition to that, before a radiant heating system is installed in an older home, the structure should have a complete energy audit done. This will ensure that the building envelope is where it should be regarding insulation, weather stripping, windows, etc. It makes no real sense to install an energy efficient system if all that energy is going to go out the window anyway.

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12 Nov 07 | Conservation, Environment, Geothermal, Solar Hot Water | Comments (0)