Taking advantage of solar energy

[banzai17]

I have a conventional central heating system using a Worcester 24cdi combi boiler, supplying heating and hot water.

I intend to have about 3.5kW of solar PV panels installed. To take advantage of the 'free' electrical energy available during the day, would it be possible to install a copper storage cylinder ? This would be connected to the consumer unit via a thermostat as per normal. However, I would appreciate advice re the plumbing.

Bearing in mind that the feeds are usually under gravity pressure from a header tank ( which I obviously don't have ), can I connect in a mains cold water feed and take off from the top into the hot water system ?

Is the pressure too high ? Is the pressure the same top and bottom so no flow when a HW tap is opened ?

Sorry to be clueless :tounge_smile mech engineer ). An info gratefully received.

 

[PlumbBobBob]

welcome to the forums. no you can't use a vented cylinder with mains feed water. you can have an unvented one though but the price is quite a lot higher and it has to be fitted by a suitably qualified engineer.

 

[banzai17]

welcome to the forums. no you can't use a vented cylinder with mains feed water. you can have an unvented one though but the price is quite a lot higher and it has to be fitted by a suitably qualified engineer.

Thank you Steveb for your reply. I would consider having this fitted ( by a qualified engineer) if the numbers worked out.
Could you briefly explain the difference between vented and non vented cylinders....vented to atmosphere ? Thanks again......Al

 

[anz]

You'll want something like this :

http://diykyoto.helpserve.com/knowl...timmersion-with-combi-boilers-central-heating

 

[cypher007]

You'll want something like this :

Optimmersion with Combi-boilers central heating - Powered by Kayako case Help Desk Software

nice setup.

ive got a standard unvented 250l being heated via a home built energy diverter I bought as a kit, he also does ready made ones. it cost me about £1300 total. you could use the combi as a heat only boiler to a header tank fed hot water tank, I went unvented in part because I was fed up of the pressure you get from a header tank. this would be the cheapest option.

another way would be to have a heat store type setup. my friend has a thing called a boilermate 2. it has an immersion at the bottom, which hes just started feeding via his newly installed panels, then a coil from the central heating, then a coil for the hot water (fed from the mains). the tank is fed water from a header tank above the cylinder if it is drained and refilled.

 

[cypher007]

forgot to say. with my 3.975kwp setup I get hot water whenever the sun shines. like Saturday we had enough to do the dishes and take a couple of showers, and this is December. infact I found in late August, when we had the unvented fitted, and through September I was still exporting power to the grid as the tank was upto temp by about 11am.

im now looking at other ways of storing the energy during the day, so in the summer at least we can cover some of the night time background load.

 

[antdad]

I'm happy to be corrected but isn't using PV's to heat water via an immersion a flawed idea in terms of efficiency and cost? The "free" unused energy created during the day is sold back via the feed in tariff while the OP's gas combi is by far the most efficient way of heating water on demand rather than using a store.

 

[anz]

I'm happy to be corrected but isn't using PV's to heat water via an immersion a flawed idea in terms of efficiency and cost? The "free" unused energy created during the day is sold back via the feed in tariff while the OP's gas combi is by far the most efficient way of heating water on demand rather than using a store.

Not if your signed up to one of these free solar panel schemes, you only keep what you use, the unused energy is sold for the installation company who keep the profit.

 

[cypher007]

I'm happy to be corrected but isn't using PV's to heat water via an immersion a flawed idea in terms of efficiency and cost? The "free" unused energy created during the day is sold back via the feed in tariff while the OP's gas combi is by far the most efficient way of heating water on demand rather than using a store.

psst, ill let you in on a secret. at the moment the FIT for export is based on a deemed 50%. eg. you get paid 4.6p roughly on 50% of what you generate, whether you use it or not, as they don't actually measure how much goes back to the grid.

 

[cypher007]

Not if your signed up to one of these free solar panel schemes, you only keep what you use, the unused energy is sold for the installation company who keep the profit.

as I understand it the freebe system companies get to keep the FIT and deemed 50% export in exchange you get to use the free juice during the generation periods.

only worth doing if you haven't got the cash or are retired and might not see the end of the 20 year period, and will use most of the free juice as at home more.

p.s. there arnt many companies doing the freebe setup any more, since the FIT was decimated in 2012. funny that.