Solar thermal panels

Rosa_Damascena

I have long wanted to capture the excess heat that lands on my south facing roof and use it to cut down my energy bills. Was toying with the idea of solar thermal panels but AFAIK the energy cannot be stored? I know that the days of selling it back to energy companies is long gone, but I had hoped that there would be a means of storing it and using it at a later time (ie winter heating),

Is there anything on the horizon? Nothing mentioned here

grumbler

AFAIK, solar thermal panels just heat the water and have nothing to do with electricity. You can sort of store the energy if you have a hot water cylinder.

Rosa_Damascena

grumbler said:

AFAIK, solar thermal panels just heat the water and have nothing to do with electricity. You can sort of store the energy if you have a hot water cylinder.

That's what I thought. I just cannot believe that it is beyond the wit of man to have worked out a way to store solar energy in a cell of some description. If a novice like me has thought it then someone somewhere must be bringing it to market?

onomatopoeia99

If you have solar photovoltaic panels installed on the roof you can save on your electric bills and you can still sell any excess back.  What you can't get nowadays is the "Feed in tariff" which was a price paid to you per unit generated whether you used it or returned it to the grid.  That was intended to encourage people to get panels installed when they were much more expensive than they are today.

You can also get a big battery with an inverter that the panels can charge up during the day and it will provide electric overnight.  I have both solar PV and battery storage and my crude calculations after a year show that approximately 1/3 of my electricity consumption for a year came from the grid, a third from the solar panels directly and a third from the battery after the sun had set.  With all factors considered, based on the first year it's going to take thirteen years to get back what they cost me to get installed.

There are also a different kind of solar panels that pass water through them to heat that for your hot water tank.  I've never looked at those as I don't have a hot water tank.  

grumbler

Rosa_Damascena said:

grumbler said:

AFAIK, solar thermal panels just heat the water and have nothing to do with electricity. You can sort of store the energy if you have a hot water cylinder.

That's what I thought. I just cannot believe that it is beyond the wit of man to have worked out a way to store solar energy in a cell of some description. If a novice like me has thought it then someone somewhere must be bringing it to market?

What cell and what do you call 'solar energy'? It's thermal energy - the sun heats the water circulating in pipes in the pannel. As simple as that. Then you store the hot water.

Other types of panels can convert solar energy to electric one, that you can store in a big rechargeable battery or sell.

fwor

As grumbler says - solar thermal panels are simply heat collectors. There is nothing new about them - they were around before photo-voltaic panels were viable. I can recall looking at installing a vacuum tube collector panel (by a company called Thermomax IIRC) on the roof of my house in the 1980's. The simplest storage at that time was, as said, a hot water tank, but more sophisticated systems existed back then - for example involving underground concrete blocks with insulation all round them.

The economic viability of these systems (of storing heat) pretty much vanished when PV became cheap.

Jeepers_Creepers

There are such things as 'ThermalStores' which can do this job, but it wouldn't be cost effective at all.

They are essentially large hot-water storage cylinders, highly insulated and with numerous inlets. The idea is that if you have a few sources of heat - a log burner, solar panels, a conventional boiler, PV panels supplying an immersion heater, etc - they all feed into this one large tank and keep it hot. You then draw your CH from this cylinder when needed, and also your DHW via a coiled pipe in the tank. 

The cost would never be justified for just a few solar panels :-) 

Your solar panels should, however, do a nice job of warming up your normal hot cylinder if you have one, and then your boiler or immersion would only have to raise - top-up - the water temp up to what you require.  

Rosa_Damascena

onomatopoeia99 said:

If you have solar photovoltaic panels installed on the roof you can save on your electric bills and you can still sell any excess back.  What you can't get nowadays is the "Feed in tariff" which was a price paid to you per unit generated whether you used it or returned it to the grid.  That was intended to encourage people to get panels installed when they were much more expensive than they are today.

I think this is what I'm after. I didn't realise the feed-in price was an incentive, I thought it was a payment for the energy itself.

You allude to the price dropping, are new installations now considered to be cost-effective? Any system / installer recommendations? And importantly, would it qualify for a Dishy-Rishi grant?

ic

https://www.simpleenergyadvice.org.uk/pages/green-homes-grant
Solar voltaic for electricity does not qualify, solar thermal for hot water does.

Jeepers_Creepers

I'd assumed you meant solar thermal panels, Rosa, when you mentioned capturing the heat from your roof, but you may have been thinking of PV panels which produce electricity?

The Thermal panel is simply heated up by the sun (doesn't even have to be 'sunny') and this heat is transferred to your hot water cylinder. You typically only install 2 or 3 panels, but even that will cost £housands on a retro-fit. It'll save you - ooh, I dunno - a £undred or so per year by warming up your hot tank? Ie - not cost effective (unless you can get it done cheaply). 

The other system is PV panels and these produce electricity from light which can then be used to power anything in your home, including heating up your hot tank via an immersion heater. You usually have to fit a fair number to get a useful output - say at least 10. This used to be viable - eg a 10-year return on your money - because the gov invested heavily in it, giving generous payments for the leccy generated. That is no longer the case, but the cost has tumbled, now around half or less (~£5k for an install?). 

On a good sunny day, this can power even high-powered appliances such as washing machines, driers and cookers, but only for as long as the sun is shining brightly; power falls off rapidly on cloudy days. To take full use of this, you either need to be at home when the sun is out, time your appliances to run during the day, or else store the power in batteries. A battery also costs around £5k...

So is it worth it? No, not until either fuel prices soar or financial assistance is given.

Really, these are only worth considering as a new install - eg a new build, or a renovation - as to retro-fit them is more involved and costly.

We looked at a house recently - a converted village hall - and it was powered solely by electricity; a large bank of PV panels (at least 4kW's worth) and a battery. Their energy supplier was specifically designed for this system - they could 'pinch' any surplus power at times of high demand (even from their battery!), and would then return it at times of low leccy cost. I think I recall the annual energy bill was estimated to approach £2k (4 bed house), so this was actually not too bad in a village with no mains gas; when oil prices were high, it would have been similar to this (tho' oil is cheap at the mo').

I have to say it was tempting; as oil prices increase again, and as energy prices do ditto, this system should become quite competitive - and it's a nice feeling that it's all quiet and clean.

Bottom line - unless the gov gives grants or other incentives to add panels (of either type) to your roof, it won't be cost effective. If, however, you were carrying out a new build or complete renovation, then it should be considered.

Doozergirl

Jeepers_Creepers said:

I'd assumed you meant solar thermal panels, Rosa, when you mentioned capturing the heat from your roof, but you may have been thinking of PV panels which produce electricity?

The Thermal panel is simply heated up by the sun (doesn't even have to be 'sunny') and this heat is transferred to your hot water cylinder. You typically only install 2 or 3 panels, but even that will cost £housands on a retro-fit. It'll save you - ooh, I dunno - a £undred or so per year by warming up your hot tank? Ie - not cost effective (unless you can get it done cheaply). 

The other system is PV panels and these produce electricity from light which can then be used to power anything in your home, including heating up your hot tank via an immersion heater. You usually have to fit a fair number to get a useful output - say at least 10. This used to be viable - eg a 10-year return on your money - because the gov invested heavily in it, giving generous payments for the leccy generated. That is no longer the case, but the cost has tumbled, now around half or less (~£5k for an install?). 

On a good sunny day, this can power even high-powered appliances such as washing machines, driers and cookers, but only for as long as the sun is shining brightly; power falls off rapidly on cloudy days. To take full use of this, you either need to be at home when the sun is out, time your appliances to run during the day, or else store the power in batteries. A battery also costs around £5k...

So is it worth it? No, not until either fuel prices soar or financial assistance is given.

Really, these are only worth considering as a new install - eg a new build, or a renovation - as to retro-fit them is more involved and costly.

We looked at a house recently - a converted village hall - and it was powered solely by electricity; a large bank of PV panels (at least 4kW's worth) and a battery. Their energy supplier was specifically designed for this system - they could 'pinch' any surplus power at times of high demand (even from their battery!), and would then return it at times of low leccy cost. I think I recall the annual energy bill was estimated to approach £2k (4 bed house), so this was actually not too bad in a village with no mains gas; when oil prices were high, it would have been similar to this (tho' oil is cheap at the mo').

I have to say it was tempting; as oil prices increase again, and as energy prices do ditto, this system should become quite competitive - and it's a nice feeling that it's all quiet and clean.

Bottom line - unless the gov gives grants or other incentives to add panels (of either type) to your roof, it won't be cost effective. If, however, you were carrying out a new build or complete renovation, then it should be considered.

We're building our own house with gas available on the road.  We looked into it all and solar just doesn't pay, presently.  

The house is as insulated and airtight as it can be, keeping the heating bills down - and that cost a large amount itself!  But solar would take 20 years to pay off, with or without batteries, or using ASHP to use more of the electricity produced immediately and using 3x less energy than gas.  I did all the calcs myself (with help from the forumites at Buildhub to translate the jargon for me).  It wasn't an experience I enjoyed.  The maximum we could save was £400 a year, with optimal sunshine and an ASHP would still be 2x the energy cost of gas, without considering the much larger outlay. 

We've run piping and power to the site of a potential future air source heat pump.  When the gas boiler comes to the end of its life and our governments make it viable, we'll go the whole hog and switch to using solar and have an all-electric house.  

I don't think it's worth it at all at the moment, sadly.