Move the earth, take the heat

Duff Hart-Davis digs his own ther­mal heat­ing sys­tem. But it didn’t quite go to plan...

The Daily Telegraph - Property - - Eco-living -

Go green! Go geo-ther­mal! Get your heat from the ground be­neath you, rather than from the Mid­dle East! Stop pump­ing car­bon into the at­mos­phere! Roused by such ex­hor­ta­tions, 12 months ago my wife and I be­gan to con­sider pos­si­bil­i­ties for our 17th­cen­tury farm­house. With an oil-fired Aga for cook­ing and a boiler for hot wa­ter and cen­tral heat­ing, our fuel bill was nearly £3,000 a year – and ris­ing. Be­sides, we were con­tribut­ing sub­stan­tially to global warm­ing. So we took a few deep breaths and called in Eco­v­i­sion Sys­tems, a young com­pany that has done ex­ten­sive re­search into ground-source heat­ing.

The prin­ci­ples are sim­ple. The Earth acts as a gi­ant heat-store, cap­tur­ing the warmth of sun, wind and rain. At 1.5 me­tres be­low the sur­face of the ground in Bri­tain, the tem­per­a­ture fluc­tu­ates be­tween 4C in win­ter and 16C in sum­mer. Pipes con­tain­ing wa­ter and anti-freeze col­lect the la­tent heat and trans­fer it to a heat pump, or com­pres­sor, which boosts the tem­per­a­ture to pro­vide hot wa­ter and cen­tral heat­ing.

The sys­tem uses a small amount of elec­tric­ity, pro­duces no car­bon and needs min­i­mal main­te­nance. If – as is claimed – it re­duces our fuel costs by be­tween 50 and 70 per cent, it will pay off our out­lay of £16,000 in less than 10 years. Be­sides, we shall qual­ify for a Gov­ern­ment grant of £1,200. Mon­day D (for dig­ging) Day. At 0800 three ve­hi­cles sweep into the farm­yard, driven by Bob Cossins, boss of the dig­ging team, Nick and Luke, who is on the dump truck.

Out in our mid­dle pad­dock are five trenches, each 50m long, into which will go the slinkies – coiled pipes con­tain­ing wa­ter and an­tifreeze – that will lead to a main col­lec­tion point.

Mov­ing fast and talk­ing faster, Bob sprays a thin line of blue dye along the track of each trench. Old maps show that this slop­ing field was once a cider or­chard but we’ve never known what lies be­neath the sur­face. Old drains? Bones? Clay? Rock? Ro­man re­mains? 0920 Two dig­gers – Big Yel­low and Lit­tle White – crawl up the field. Their buck­ets bite into the an­cient turf. Up comes 8-10in of fine top­soil. The layer be­neath is brashy – crumbly clay flecked with white grit. Be­low that is solid clay. 1430 A huge truck grinds up the lane with the first load of sand for lin­ing the trenches. With a vast, deep hiss, 16 tons slides out. 1545 The first trench is fin­ished, 2m deep and only 30cm wide. Sidling along it, I get an odd feel­ing think­ing that no hu­man feet can ever have walked on this level be­fore. Tues­day 0800 Heavy rain in the night causes trench col­lapses, en­tail­ing much ex­tra ex­ca­va­tion. 1045 An orange van de­liv­ers the slinkies, each one 250m of tough 32mm black poly­eth­yl­ene pipe, tied in loops 1m in di­am­e­ter. 1430 We lower the first slinky into its long home. The dig­ger driv­ers pour sand on to the pipe so that it is snugly bed­ded. Once it’s cov­ered, the rest of the trench can be back-filled with soil. 1545 Thun­der crashes over­head. A down­pour sets in. The dig­gers slide around, spread­ing greasy clay.


Wed­nes­day 0930 Martin All­man, busi­ness man­ager of Eco­v­i­sion Sys­tems, ar­rives to check progress, along with Mark Witzen­berger, his tech­ni­cal ex­pert from Ger­many, where ground-heat­ing sys­tems have been in use for 25 years. Martin takes a rad­i­cal de­ci­sion: be­cause of the weather and the clay, the other trenches will have to be wider and shal­lower, with the slinkies laid hor­i­zon­tally. So long as they are 1.2m be­neath the sur­face, their ef­fi­ciency will be unim­paired. Thurs­day Ross Ver­ity, mas­ter plum­ber, tests the first slinky by fill­ing it with wa­ter and pump­ing up the pres­sure to twice that of a car tyre. Fri­day Our equip­ment is de­liv­ered: heat pump – like a big up­right fridge – hot-wa­ter tank and ex­pan­sion tank. It’s all branded Dim­plex, the Ir­ish firm, but – be­cause it’s made in Ger­many – it car­ries Ger­man la­bels. Mon­day A new dig­ger-in-chief, Paul, has a vel­vet touch on the con­trols. As he back-fills the trenches, he clears earth and clay off the sur­viv­ing turf with mar­vel­lous del­i­cacy. Tues­day Chaos! Ross whacks into the plumb­ing. Out comes the old hot-wa­ter cylin­der, so there’s no wa­ter in the house. In the field, the dig­gers’ buck­ets rat­tle and clank as they ex­ca­vate a 2m-deep pit in which the slinkies will unite. In the hole, Bob starts build­ing a sur­round of con­crete blocks to house the man­i­fold. Wed­nes­day Fine and hot, but the chaos in­creases. A sec­tion of fence comes down to ad­mit Lit­tle White into the gar­den. A tur­f­cut­ter slices a path di­ag­o­nally across the lawn – agony for the gar­dener (my­self, nat­u­rally). Thurs­day Work­ing on the pit. By evening, Ross has all the slinkies con­nected up. Fri­day In the gar­den, Lit­tle White digs a trench for the 63mm flow-and-re­turn pipes con­nect­ing the man­i­fold to the heat pump. Paul probes del­i­cately to find the sewer. In spite of his care, his bucket cracks the old clay duct and a sec­tion has to be re­placed with plas­tic. No flush­ing for the du­ra­tion. Sud­denly the dig­ger is just 4ft from the front door. Up comes the con­crete path, in jagged slabs. Great heaps of clay hem us in. We’re be­ing at­tacked from all sides. “Trench war­fare,” says Martin jovially.

Unan­nounced vis­i­tors ar­rive, ea­ger to see the show. They’re ap­palled by the dev­as­ta­tion. “Fear not,” I tell them. “It’s the new gar­den­ing.” But in­wardly I feel that things can’t get any worse. Mon­day They do. We clear the util­ity room. Car­pet, boots, coats, books, box-files, spin-drier – all out and into my study. When Ross cuts a chan­nel through the floor tiles with a grinder, the dust is in­cred­i­ble. From out­side, it looks as though the house is on fire: dense white clouds bil­low from the win­dows.

We feel like we’ve been dragged into run­ning a marathon. The only sav­ing grace is that our whole team is so lively, con­fi­dent and cheer­ful. Tues­day Ross bores a tun­nel un­der the house wall. By evening, the 63mm pipes, heav­ily in­su­lated, are buried un­der a new screed. Wed­nes­day He grap­ples with the maze of cop­per pipes, wheel-valves and sen­sors be­hind the heat pump. When asked how it’s go­ing, he in­vari­ably replies, “Cool!” Thurs­day The house is alive with elec­tri­cians – three of them, two called Roger, rang­ing through the rooms like fer­rets. Fri­day Mark spends hours pro­gram­ming the heat pump’s elec­tron­ics. The util­ity room is again un­der siege, with bright blue fluid cours­ing through coils of trans­par­ent pipe as Ross pumps gly­col into the ground sys­tem. Mon­day Count­down! Fi­nal ad­just­ments all morn­ing. Then, at 1428, Mark switches on. The pump hums into life. Ten sec­onds later, with a death rat­tle, it shuts down. Curses! Have the Earth deities struck back at us for vi­o­lat­ing their abode? Not so. Ross di­vines the trou­ble and, at the sec­ond at­tempt, away the pump goes. “Cool!” he cries. But for once he’s wrong. Things aren’t cool: they’re hot. The in­com­ing flow from the ground is at 16C: the flow up into the cylin­der is at 55C. Magic! All over the house the ra­di­a­tors spring into life. The wa­ter in the taps is soon too hot to han­dle. Tri­umph! We’ve gone green – and our neigh­bours are green with envy.

Eco­v­i­sion Sys­tems, Dream House, Lam­pern Hill, Uley, Durs­ley, Glos (01453 861354;­v­i­sion sys­ Econic, 9 Cot­man Road, Nor­wich (01603 700999; www.econ­i­ Earth En­ergy, Fal­mouth Busi­ness Park, Bick­land Wa­ter Road, Fal­mouth (01326 310650; en­ergy. Earthwise Scot­land, Nether­ton Busi­ness Cen­tre, Kem­nay By In­verurie, Aberdeen­shire (01467 641640,­wis­escot­

Warm­ing up: Duff Hart-Davis (in striped shirt) and Martin All­man, of Eco­v­i­sion Sys­tems, pre­pare trenches for the wa­ter and anti-freeze filled heat­ing pipes, which col­lect la­tent un­der­ground heat

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