Solar thermal eclipsed by PV: Can Epsom salts revive industry and solve storage?


“My work tends to be driven by what might be the right solution in the future, even if it is not cost effective at the moment,” says Sansom. Decarbonising heat is “difficult in the short term, but there are technologies and approaches that government could incentivise to speed up that change”.

Sansom has “no doubt” heat could be decarbonised within “five to ten years if we decided as a nation that is what we wanted to do”. Technically, he says, “it is not that difficult”.

Waste heat is the “obvious place to start”, he says, citing the number of large power stations cited next to significant conurbations. While there is an efficiency tradeoff between electricity and heat for combined heat and power, Sansom thinks it would be worth it.

He thinks heat storage is also overlooked.

“Somebody once told me it is much easier to store heat than electricity,” says Sansom. “I have built my career on that statement. It is very easy to store heat.”

While average immersion heaters can store hot water for six to eight hours, Sansom is working on seasonal heat storage. He thinks that every house in the UK could store enough energy from the sun to service heat and hot water requirements all year round.

“Enough energy falls on my roof in Northampton, right in the middle of the country, so that 6,7,8 square meters of solar thermal panels will heat my home and provide hot water all year round,” says Sansom. “That is fact, I’ve worked it out.”

“Of course, it all comes in the summer and I want all my heat in the winter.”

A dose of salts

But Samson believes the answer to solar thermal storage is not far away. He thinks it could shift the balance of power between solar PV and its poor thermal relation.Epsom-salts_tablespoon

The solution? Magnesium Sulphate Heptahydrate, otherwise known as Epsom salts, universally used to treat indigestion, muscle aches and, ironically, sunburn.

“If you heat it, dry off the water, keep it somewhere dry, go back a few months later and add some water to it, it will get up to about 80 degrees C,” says Sansom.

Whereas hot water stores around 150mj/M3, he says the Epsom stores around 2000mj/M3. His students are building seasonal storage units “about the size of a small shed… something you would put in your garden or loft.” And that is with standard, off the shelf solar thermal panels. More advanced panels he says, “will reduce the footprint further”.

But is it simply theoretical technology? Sansom says not. He is currently working with a property developer to trial the technology “at the three or four house level” and is writing proposals for Innovate UK and European funding. But he thinks an almost insignificant amount of extra government help “could be a game changer, much as I hate to use the term.”

“We are not doing basic research any more. We are building this system to serve several houses. And once you build a demonstrator and show people that it works in reality, the commercial guys all come in.”

Sansom thinks a tightly directed fund from Decc or Innovate UK for applied research “right up to a demonstrator with a company-led commercial plan at the end of it as part of the call” would cost no more than “a few hundred thousand pounds” or “low millions” to fund several projects.

“That is the stage we are at,” he says. “It really isn’t that far away.”

Pluck low hanging fruit

Asked where he sees the the other easy wins in decarbonising heat, Samson cited waste heat as potentially the biggest wasted resource.

“Low hanging fruit should certainly include waste heat from industrial processes and power stations,” rugeleysays Sansom. ”There is no reason why [for example] Rugeley – a massive power station – could not be heating the town. And there are a lot of towns with big power stations next to them. It really is easy to get that heat into their homes.”

He also thinks excluding waste heat from renewable subsidies is a mistake. “That’s an odd one. I don’t really understand it.”

But he returns to solar thermal as potentially the easiest way to decarbonise heat at point of use.

“It has been the poor relation behind solar PV. But if you want heat, the heat is there. There is no reason not to do that, but we lack the economy of scale, the cost curve that solar PV has experienced, where everything halved in price every year. There isn’t the demand for solar thermal panels. Yet.”

Industry the exception

If the UK is serious about decarbonising, Sansom thinks gas could be gone “within five to ten years.” But industry will be the exception. “Heavy industry uses a lot of heat. It is a tough one and I haven’t got an easy answer.”

heatreportsmalChris Samson is one of a number of experts interviewed for their views on decarbonising heat in Energyst Media’s new heat report. It’s free to download and also contains a survey of readers on the technologies they are deploying, their views on heat incentives and whether the ErP directive is swaying their purchase decisions. Download it here

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