YOU probably would not want to go swimming in Hinksey Lake without a thermal layer.

And yet there is enough latent heat stored in there to heat nearly 100 houses, the local primary school and Hinksey Outdoor Heated Pool.

That is according to Oxford’s Low Carbon Hub, which has just completed a technical feasibility study into the idea.

All the users could potentially get cheaper heat, but more importantly to the hub, they could cut their combined carbon emissions by 75 per cent.

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Hub project officer Adriano Figueiredo describes Hinksey Lake as a “huge battery” with energy just going to waste.

“The lake is about 4,000 square metres – it is a huge battery.

“There’s so much heat in there, even if you extracted two degrees from the water you can heat it up by much more on the other side.”

Under the proposed scheme, the hub would run several kilometres of water-filled pipes into the lake. Deep in the lake, the water in the pipes would pick up the two degrees of heat from the surrounding water.

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The outdoor pool

The pipes then go into a heat exchanger, which Mr Figueiredo describes as a “fridge but in reverse”.

He said: “With a fridge you’re basically taking the heat from inside the box and exchanging it with the air around to pump the heat out. We would be doing the opposite: taking the heat from the water in the lake by circulating the water in the heat exchanger.

“We keep warming up until it’s much hotter than the lake itself.”

That process can heat the water in the pipes up to 55 degrees, and what is more, Mr Figueiredo added: “It’s a very energy-efficient way of doing it”.

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The pump could be potentially be powered by solar panels, making the whole system even lower on carbon emissions, but even if it used electricity from the grid, the system would produce a fourfold return on energy input in the form of heat.

The hub’s technical feasibility study showed such a system could heat the outdoor swimming pool, the school and 95 homes in between on Lake Street, part of Gordon Street and part of Vicarage Road Part of the beauty of it is that the outdoor pool would only need to be heated in the summer and the homes would need the most heat in the winter.

Hooking up more homes would be possible but has not yet been looked into, and getting the heat pipes into all those homes would mean digging up the road – which could prove both costly and logistically difficult. The whole district heat network could be owned by the residents themselves, if they wanted to invest in it, in the same way that Osney Lock Hydroelectric power plant on the River Thames is owned by 200 shareholders who invested a combined £640,000.

With the success of their technical study under their belts, the hub team is now embarking on the next phase – a financial feasibility study.

That will examine different models of ownership, possible sources of electricity, potential carbon emission savings and the cost of digging up roads.

Both studies have been enabled by a £20,000 grant from the Government’s Urban Community Energy Fund.

Mr Figueiredo added: “We’re learning a lot from doing this study and it will be made available so the whole county can use what we’ve learned.”