| I don’t think
that there is any doubt that the days of cheap oil are probably
gone. Most experts have different opinions about where the oil
prices are going, but some are estimating that oil will reach
$100 per barrel sometime in the near future.
The price of natural gas is also on the way
up. With oil prices rising, many manufacturers are switching
to natural gas, which means less gas for residential customers.
In addition, natural gas is being used to generate electricity
because it burns cleaner, placing even more pressure on the
natural gas market and prices.
Natural gas has been a favorite source of energy
for commercial and residential buildings for many years because
it has historically been less expensive than electricity for
heating. Now that natural gas prices are increasing, an alternative
solution that has been available for many years is getting more
attention, and that is the geothermal system.
There are basically two kinds of geothermal
systems, pond-coupled and ground-coupled. Each system works
in a similar fashion, using a heat pump with a loop that is
run through a medium (in this case either water or earth).
The temperature of soil and groundwater at around
6 feet below the surface stays at a fairly constant level, somewhere
between 45 and 55 degrees farhenheit.
In the winter, heat is extracted from the ground
using a heat pump. Using a heat exchanger, this heat can be
transferred into a building via the forced air system.
In the summer, the heat pump is run in reverse,
extracting heat from the building and transferring it to the
ground. Using the same heat exchangers, air in the forced air
system is cooled by the loops coming from the medium.
In both the pond and ground coupled systems,
a loop of piping containing a fluid (either water or anti-freeze)
that circulates through the heat pump is installed in a pond
or the ground. The piping is made of high-density polyethylene,
which is warranted for 40-50 years.
Piping for the pond-coupled system needs to
be about 15 feet below the surface of the water to reach stable
temperatures, and an acre pond is sufficient to heat and cool
a building containing 6,000 to 8,000 square feet. If the pond
has a tendency to go dry during hot weather or drought, a water
well may be required to keep the pond full enough to be operational.
Pond-coupled systems can work in conjunction
with stormwater management. Since many cities now require that
stormwater be detained on site, a “wet” detention area can serve
as the water source for the pond-coupled system. Dry detention
areas are designed to hold a certain quantity of water during
periods of heavy rain. A wet system works the same way, except
it is designed to hold the same overflow on top of the permanent
body of water in the pond.
There are two kinds of ground-coupled geothermal
systems, vertical and horizontal.
Vertical systems require wells to be drilled,
sometimes up to 300 feet deep. Larger systems may require multiple
wells, so this is the more expensive of the two. Vertical systems
are usually used where there is not sufficient space to do a
horizontal system.
Horizontal systems require that the loops be
buried in 6 foot deep trenches. These systems require about
one square foot of land per one square foot of building to work
properly. They can be installed in open fields or under parking
lots, and because the piping is so tough, they require little
maintenance.
The initial cost of geothermal systems is higher,
but their operating costs are lower. Some experts estimate that
they are about 25 to 40 percent more efficient than other systems,
and that they will pay for themselves in six to eight years
of operation.
The primary advantage of using this kind of
system is that it uses electricity to run the system. The power
that comes from the grid can be generated by the burning of
oil, gas or coal, or it could come from other sources such as
nuclear, hydroelectric, wind power, or (someday) even photovoltaics.
The utility company buys the cheapest source of electricity
that it can, so the savings can be passed on to the consumer.
If a heating and cooling system is designed
to only burn gas, it has only two choices – natural gas or propane,
each of which are probably going to go up in price.
Churches and other building owners need to begin
looking at this not-so-new technology when constructing new
facilities or when replacing old HVAC systems. It could eventually
result in huge cost savings if properly designed and operated.
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