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There is a vast quantity
of free, clean, and renewable energy in our ponds, oceans, and
the waters that surround the Vineyard. Through the use of geothermal
heat pumps, we can collect and concentrate this low grade stored
solar energy into high grade energy to heat and cool our buildings.
This energy is available 24 hours a day all year long.
Because the Sun is storing this energy for free, a geothermal
heat pump can typically collect 2 to 4 units of free energy for
every unit of energy put into the heat pump. The end result is
an efficiency ranging from 300 to 500%! In comparison, boilers
and furnaces are fast approaching their limit of efficiency (currently
some of them have 98% efficiency) of 100%.
Because geothermal systems are 3 to 5 times more efficient than
the best fossil fuel systems, their operating costs are about
half. In other words, the annual cost for electricity to run a
geothermal system is half the annual cost of propane or fuel oil
to run a furnace or boiler.
We proposed our ocean
based geothermal system in November 2006
and our pond based approach in September 2007.
The following sections will have additional details about the
ocean and pond approaches as well as an introduction to some ecological
and permitting issues.
We wish to describe a geothermal system that will use the stored
solar energy in a pond (or any sufficiently sized body of water)
to heat and cool a building – we call this system “pond
based geothermal”.
This system will consist of a plate type heat exchanger (SlimJim
brand) submerged in a pond (held in a vertical position and mounted
to a skid resting on the bottom), a geothermal heat pump and circulator
pump located inside the structure, and supply and return pipes
buried at a 4 foot depth connecting the heat exchanger in the
Pond and the heat pump.
We believe that there have been no geothermal installations on
the Vineyard that have used ponds (or other bodies of water) for
their source of stored solar energy. While this pond based geothermal
will be the first use of this geothermal concept on the Vineyard,
there are many successful installations of this type around the
world.
In Chicago, the Coast Guard Marine Safety Station uses a SlimJim
heat exchanger under their pier to provide all of their heating
and cooling. Even in the middle of last February with two feet
of ice on Lake Michigan, the Coast Guard station was warm and
toasty with heating provided solely by the stored solar energy
in the 37 F lake water.
The largest manufacturer of geothermal heat pumps in the world,
WaterFurnace, heats and cools their entire factory from the stored
solar energy in a man made pond in front of their headquarters
in Indiana.
The geothermal process uses energy from the Sun that is stored
in the Earth, the oceans, or the bodies of water on the surface
of the Earth. As we receive more energy in 10 seconds from the
Sun than mankind uses in an entire day, this is an essentially
limitless supply. The geothermal process connects this abundant
yet low grade energy to a heat pump which is able to concentrate
the energy and raise it in temperature to a more useable form.
Through the use of a heat pump we will be able to use the solar
energy stored in a pond to heat a building.
This geothermal concept will use a small fraction of the available
solar energy stored in the pond’s water. Sizing software will
allows us to project the amount of solar energy available in this
pond. The available energy is basically a function of the pond’s
area and its volume of water.
The amount of energy we wish to “remove” from the
pond to heat a residence will be minute compared to the constant
input of solar energy into the pond – our analysis indicates
that for a properly sized installation, there will be no measurable
effect on the pond’s temperature.
The heat exchanger (herein called the SlimJim) is a stainless steel
or titanium welded plate type device used to exchange heat between
the pond water and a closed geothermal loop. The SlimJim is formed
by welding and pressing two plates of stainless steel or titanium
together – each assembly is pressure tested and fitted with
inlet and outlet pipe connections. Nominal dimensions of a 5 ton
capacity (60,000 Btu/hr) unit are 4’ in height, 8’ in
length, and ½” thick with a weight of 100 pounds. This
heat exchanger plate may then be suspended under a pier, suspended
below a float, or mounted on skids for pond-bottom locations. There
is an absolute barrier between the pond water and the closed geothermal
loop – the system is designed to be leak free over its entire
life expectancy of 50 years (or more).
A typical installation would involve placing the SlimJim in the
deepest part of the pond – it is recommended that at least
two feet of unfrozen pond water be above the SlimJim at all times.
The geothermal heat pump will be located in a mechanical room
and will be connected to the buildings heating and cooling system.
The advantage of a geothermal system is that it replaces direct
use of fossil fuels and has an efficiency on the order of 400%
- for every unit of electricity put in the system outputs 4 units
(because the sun has given us three units for free into the pond).
This means that typical operating costs are up to 50% of a gas
or oil system. Once a geothermal system is coupled with electricity
generated by a renewable source, as wind or solar PV, the carbon
footprint of the project shrinks to zero.
The pipes that connect the SlimJim to the heat pump with be black
polyvinyl (HDPE) well water tubing of 2” in diameter. They
will be buried at a 4 foot depth from the house to the SlimJim.
The pipes can be installed with a trenching machine to reduce
disturbance of foliage to a minimum.
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