[LINK] Geothermal wells

[stephen at melbpc.org.au]

Geothermal energy systems, common in countries like Iceland and China, 
use the constant temperature of the earth to heat and cool buildings. 

Geothermal wells are dug to a depth where the earth regulates the 
temperature of water or a liquid circulating through the system. 

Geothermal systems may require one well, or dozens, to regulate a 
building’s temperature, depending on the size of a building and type of 
system installed. While the systems are called wells, they are actually 
an underground network of pipes connected to heat pumps to circulate 
water or some other liquid. 

Because digging geothermal wells can be expensive and logistically 
difficult, the systems have been slow to catch on. Yet, according to the 
Rockefeller Foundation and DB Climate Change Advisors, “buildings consume 
approximately 40 percent of the world’s primary energy and are 
responsible for 40 percent of global carbon emissions.” 

Installing a geothermal system can significantly reduce a building’s 
carbon footprint, and over the last decade, the number of geothermal heat 
pump systems has grown steadily. More geothermal systems are installed in 
New York, New Jersey and Pennsylvania than anywhere else in the United 
States. 

In all, more than 100 geothermal projects are in operation in the five 
boroughs, and about 90 percent of those projects are what are known as 
closed loop vertical bore systems, Mr. DiEnna said. A closed loop system 
is sealed from the ground and liquids are reused within the system, while 
an open loop system has discharge water it releases into a ground well or 
surface water. 

In New York, “the biggest obstacle currently to geothermal energy is the 
initial cost, which can be more significant than a traditional furnace 
replacement,” said Daniel Goodwin, a mechanical engineer with the Miller 
Environmental Group. 

However, Mr. Goodwin points out that since geothermal systems both heat 
and cool, they can replace not just the heating system but the cooling 
system as well. 

It makes the most sense to install a geothermal system in new 
construction, especially given incentives and federal tax credits for 
geothermal, he said. “If you’re retrofitting a building, it’s going to be 
an initial cost,” Mr. Goodwin said. “But from a new construction 
standpoint, when you look at the numbers and the tax credits and things 
out there, it really becomes a no-brainer.” 

A geothermal heat pump system, if installed correctly, can cut the annual 
energy bill of a building by 30 to 60 percent, said Zoe Reich, an 
environmental specialist who heads the sustainability department at the 
engineering firm Edwards & Zuck. The typical payback period for 
geothermal systems in New York is two to eight years, factoring in any 
financial incentives or tax credits, Ms. Reich said. 

If the proper system is installed, then not only does it save money in 
operations, but also in maintenance, Mr. Goodwin said. “Since there’s no 
combustion, there’s no carbon fouling due to the burning of fossil fuels, 
it’s easy to maintain,” he said. 

Also, the pipes in a closed loop vertical bore well system are warranted 
for 50 years, while the aboveground geothermal equipment has a life 
expectancy of 25 to 30 years, Mr. Goodwin said. That’s roughly twice the 
life expectancy of a furnace or other conventional system, he said. 

A 3,000-square-foot home in a suburban area would probably need two to 
three wells, at $9,000 per well, for a geothermal heat pump system to 
heat and cool the home. 

<http://www.nytimes.com/2012/11/07/business/geothermal-energy-advocates-
hope-systems-get-a-second-look.html?>

Message sent using MelbPC WebMail Server