En­ergy & re­new­ables

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Ground source heat pumps (GSHPs) use pipes which are buried in the gar­den to ex­tract heat from the ground. This heat can then be used to heat ra­di­a­tors, un­der­floor or warm air heat­ing sys­tems and hot wa­ter in your home.

A ground source heat pump cir­cu­lates a mix­ture of wa­ter and an­tifreeze around a loop of pipe, called a ground loop, which is buried in your gar­den. Heat from the ground is ab­sorbed into the fluid and then passes through a heat ex­changer into the heat pump. The ground stays at a fairly con­stant tem­per­a­ture un­der the sur­face, so the heat pump can be used through­out the year.

The length of the ground loop de­pends on the size of your home and the amount of heat you need. Longer loops can draw more heat from the ground, but need more space to be buried in. If space is lim­ited, a ver­ti­cal bore­hole can be drilled in­stead.

The ben­e­fits of ground source heat pumps

• Could lower your fuel bills, es­pe­cially if you re­place con­ven­tional elec­tric heat­ing

• Could pro­vide you with in­come through the gov­ern­ment’s Re­new­able Heat In­cen­tive (RHI)

• Could lower home car­bon emis­sions, depend­ing on which fuel you are re­plac­ing • No fuel de­liv­er­ies needed • Can heat your home as well as your wa­ter

• Min­i­mal main­te­nance re­quired

Un­like gas and oil boil­ers, heat pumps de­liver heat at lower tem­per­a­tures over much longer pe­ri­ods. Dur­ing the win­ter they may need to be on con­stantly to heat your home ef­fi­ciently. You will also no­tice that ra­di­a­tors won’t feel as hot to the touch as they might do when you are us­ing a gas or oil boiler.

Air source heat pumps are

usu­ally eas­ier to in­stall than ground source as they don’t need any trenches or drilling, but they are of­ten less ef­fi­cient than ground source heat pumps. Wa­ter source heat pumps can be used to pro­vide heat­ing in homes near to rivers, streams and lakes.

Find case stud­ies and ex­am­ples of home­own­ers who have in­stalled a ground source heat pump us­ing our Green Homes Net­work.

How do ground source heat pumps work?

Heat from the ground is ab­sorbed at low tem­per­a­tures into a fluid in­side a loop of pipe (a ground loop) buried un­der­ground. The fluid then passes through a com­pres­sor that raises it to a higher tem­per­a­ture, which can then heat wa­ter for the heat­ing and hot wa­ter cir­cuits of the house. The cooled ground-loop fluid passes back into the ground where it ab­sorbs fur­ther en­ergy from the ground in a con­tin­u­ous process as long as heat­ing is re­quired.

Nor­mally the loop is laid flat or coiled in trenches about two me­tres deep, but if there is not enough space in your gar­den you can in­stall a ver­ti­cal loop down into the ground to a depth of up to 100 me­tres for a typ­i­cal do­mes­tic home. Heat pumps have some im­pact on the en­vi­ron­ment as they need elec­tric­ity to run, but the heat they ex­tract from the ground, the air, or wa­ter is con­stantly be­ing re­newed nat­u­rally.

Is a ground source heat pump suit­able for me?

To tell if an air source heat pump is right for you, there are a few key ques­tions to con­sider:

• Is your gar­den suit­able for a ground loop? It doesn’t have to be par­tic­u­larly big, but the ground needs to be suit­able for dig­ging a trench or a bore­hole and ac­ces­si­ble to dig­ging ma­chin­ery.

• Is your home well in­su­lated? Since ground source heat pumps work best when pro­duc­ing heat at a lower tem­per­a­ture than tra­di­tional boil­ers, it’s es­sen­tial that your home is well in­su­lated and draught-proofed for the heat­ing sys­tem to be ef­fec­tive.

• What fuel will you be re­plac­ing? The sys­tem will pay for it­self much more quickly if it’s re­plac­ing an elec­tric­ity or coal heat­ing sys­tem. Heat pumps may not be the best op­tion for homes us­ing mains gas.

• What type of heat­ing sys­tem will you use? Ground source heat pumps can per­form bet­ter with un­der­floor heat­ing sys­tems or warm air heat­ing than with ra­di­a­tor-based sys­tems be­cause of the lower wa­ter tem­per­a­tures re­quired.

• Is the sys­tem in­tended for a new devel­op­ment? Com­bin­ing the in­stal­la­tion with other build­ing work can re­duce the cost of in­stalling the sys­tem.

To find out more, please visit http://www.en­er­gysav­ingtrust.org.uk/re­new­able-en­ergy/heat/ground­source-heat-pumps

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