You may remember a few months back I took a look at the pros and cons of geothermal energy.
In other words, tapping into the potentially limitless heat energy that's available beneath
the surface of the earth. We looked at very large systems providing grid scale energy,
like the one in Iceland, and very small domestic systems that provide just enough heat to run an
individual home. The biggest drawback of those domestic systems is that they're often fitted
retrospectively to existing houses and as a result they can be prohibitively expensive.
Just like every other element in the building industry, a geothermal heating system
is far easier and less expensive to install if it's done before the house is built in the
first place. That way all the architectural and technical specifications can be designed correctly
right from the get-go. And sure enough there are plenty of examples of far-sighted environmentally
conscious self-builders who've done just that for their own house projects. But even with this level
of planning and preparation, installing all that underground infrastructure just for a single home
still lacks the economy of scale achieved by utility-sized operations. So perhaps there's
a potential gap in the market here. What if a system could be implemented that did have similar
economies of scale to those enjoyed by grid scale operators but that still retained the direct
flexibility and control enjoyed by individual homeowners? Well that's exactly what's happening
in a housing development called Whisper Valley just outside Austin, Texas in the U.S, and it
looks like it could be a blueprint for developers all over the United States and the wider world.
Hello and welcome to just have a think. You folks across the pond will know much better than me that
large-scale residential and mixed-use housing developments, which can include thousands of
new homes, are common in the United States. They're called master-planned communities,
and in many ways this one in Whisper Valley is a fairly typical example. When it's all
finished it'll comprise five thousand houses of various sizes, two and a half thousand apartments,
and two million square feet of commercial space along with schools community buildings and even
a wastewater treatment plant catering for 30 000 residents. The whole thing will be the size of a
small town covering a total area of 2000 acres. The big difference is that all the buildings on
this development will have the potential to produce as much electricity as they consume,
thanks to a ground-breaking geothermal and solar power system provided by a company called Ecosmart
solution. A geothermal exchange loop field known as a geogrid system provides the bulk
of the thermal energy for heating and cooling and even domestic hot water. Unlike large geothermal
systems that use high temperature sources typically from deep locations within the earth
for electricity generation, geothermal exchange loops in combination with ground source heat pumps
provide a highly efficient renewable energy technology that pumps thermal energy from the
earth directly into the buildings in the winter and then reverses that flow in the summer. That's
combined with ultra efficient appliances and smart thermostats to reduce the energy requirements of
each home by about 65 percent. And all those smart home technologies can be controlled
by an app and portal that can integrate more than 10 000 different devices or products
with an energy monitoring platform from a company called Sense that enables homeowners to have
complete control over how they allocate their energy expenditure. It's a very clever setup,
and plus as a nice little aside - and in a rare example of common sense and lateral thinking -
while Ecosmart have the trenches open to put in the geothermal pipework, they also run fibre optic
cables in there too, which provide gigabit per second internet speeds for every single house.
The geothermal system works in conjunction with rooftop solar panels and in some cases
with home battery storage systems to manage electricity use and to provide backup power
in the case of a power outage. Ecosmart call that a power resiliency package.
The installed solar PV systems on each house only need to be relatively small because of the lower
electricity demand as a result of the geothermal system, and all the homes are zero energy capable
which means that homeowners enjoy very low or even zero utility bills with what's called smart
energy behaviour. The geothermal system itself uses polyethylene pipes with a 50 year warranty.
Each home is equipped with its own ground loop in conjunction with a highly efficient geothermal
heat pump to take advantage of the earth's 22 to 23 degrees Celsius year-round temperatures
in Austin. The vertical ground loop is inserted into a 350 foot deep bore hole.
Water passing through the pipe absorbs or emits heat energy depending on the season.
The heat pump then uses that to either heat or cool the home. What makes Whisper Valley's
geothermal system innovative is that each home's vertical ground loop is networked into the main
geogrid communal underground system. That's five miles of pipework with an energy centre that
provides central pumping, ancillary heat rejection through cooling towers, and advanced monitoring
and control enabling the entire development to share and optimize thermal energy. That's very
useful because it provides a bit of resiliency if anything goes wrong with an individual borehole,
and it also means that the geothermal capacity of an individual home doesn't need to be sized
to the home's peak load. And the entire geogrid for each development phase is installed before the
first home is even under construction. That makes it very easy for the builder in Whisper Valley
to simply hook up to the geogrid, very similar to connecting to the water supply.
Heat is extracted from the boreholes between December and early March so there's ample
thermal capacity to absorb the heat rejection from the homes during the summer and autumn,
when the ground source heat pumps gradually increase the borehole temperatures back up again.
The central monitoring software controls the performance of the underground system and the
cooling tower to ensure that the geothermal water doesn't exceed the maximum temperature, and to get
the most efficient performance out of the ground source heat pumps. Did I mention it was very
clever? Ecosmart say that as they gain empirical data from the operation of the geogrid system
their engineers will be better able to predict its thermal dynamics to build in improvements as each
phase of the development unfolds. They're working to an industry standard benchmark called the home
energy rating system, or HERS, which is set up by the U.S residential energy services network or
RESNET. The target for homes on the Whisper Valley development is a HERS rating of 25 or lower.
That means the building would consume 75 percent less energy than a standard conventionally
built heated and cooled new home. The lower the number goes the better the home efficiency is,
and the lowest HERS rating so far achieved in Whisper Valley is seven. Which is pretty good!
Homeowners are currently eligible for tax incentives on the geothermal installation
as well as their homes solar panels and batteries. That allows them to write off 26
percent of the value of both systems, which can be anything between six and fifteen thousand dollars
depending on the size of the home. Ecosmart then charge each household a small fixed monthly fee
of between 50 and 70 dollars to pay for all their services. As of May 2021, Whisper Valley had 207
occupied homes, and another six under construction as part of the full 237 homes in phase one.
The infrastructure for phase two is complete, and that'll be 267 more homes. Phases three and four
will add a further 363 homes during 2021 and 22. On average the builders sell about one
house per day, and the demand for Ecosmart homes is proving to be very high. In total there are
a brain bending 51 phases on the development, with an estimated final completion date of 2035,
which makes me very glad I'm not a project manager anymore! But if you're an American watching this
then you'll be pleased to know that most of the components of the geogrid systems
are manufactured and assembled in the USA, which means yet another example of an opportunity to
create the decent well-paid jobs that'll be such a crucial element, not just of President Biden's
ambitious green recovery program for America, but of the entire global transition to a cleaner,
more sustainable future. No doubt you'll have views on this initiative too. If you do,
then jump down to the comment section below and leave your thoughts there.
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