Solar power on roofs - more viable with energy price hikes?

[Ubique]

One thing that always seemed a waste of energy is the hot water that sits in the pipes, just to go cold - and then get pushed out by more hot water... rather than have a hot water cylinder or a combi boiler, a point-of-use water heater would surely be more efficient - and quicker. I know it's only around 150ml/m for 15mm pipe but over a week, it's a lot of wasted hot water.

 

[Trevorleach]

Thanks! I know how long it takes for people start moaning about cold water! About 1 long showers worth
I only have a 120 litre cylinder atm but have beefed up the joists in the tank room to take a much bigger cylinder! Just don't know weather to go for solar thermal or PV.
PV seems more versatile.

It would be interesting to hear from others with PV just how well their system heats the hot water at different times of the year?

 

[Gareth J]

Thanks! I know how long it takes for people start moaning about cold water! About 1 long showers worth
I only have a 120 litre cylinder atm but have beefed up the joists in the tank room to take a much bigger cylinder! Just don't know weather to go for solar thermal or PV.
PV seems more versatile.

That sounds about right to me.

If the logistics suit, you can put in a second cylinder that feeds into your first. Then, you can get your diverter to heat the small, original tank, first, then, if that's hot, flip to heating the second, bigger, tank. Via a thermostat, relay and a bit of simple wiring - have done a few times, will explain if you go that route.

Regarding solar thermal Vs PV, I'm of the opinion that PV is so, relatively, inexpensive, easy to fit and has the ability to be useful as electric too, it's an easier decision to just fit even more PV. But that's my opinion - others are fans of thermal. Makes a difference whether you prefer wiring or plumbing too I guess!

One thing that always seemed a waste of energy is the hot water that sits in the pipes, just to go cold - and then get pushed out by more hot water... rather than have a hot water cylinder or a combi boiler, a point-of-use water heater would surely be more efficient - and quicker. I know it's only around 150ml/m for 15mm pipe but over a week, it's a lot of wasted hot water.

I agree. Can be managed manually if you're a bit thoughtful - wash hands with cold water, stack dishes until there's a pan full etc.

It's only really wasted in summer though. Rest of the time it aids heating the house - unless your pipes run outside the heated world

 

[addjunkie]

We have two tanks, one for hot water the other a heat store, which in effect is our heating with currently 3 heat sources. Back boiler on log burner, oilboiler and solar pv.
We have a magic box on thesolar that diverts any spare ( all you're ex port) in to the tanks. Hot water first then thermal store. This is the magic box https://myenergi.com/product/eddi/
All it basically does is ensure all you generate is used.
Has it reduced the heating bill, cant say, very difficult to monitor with oil prices fluctuating and also burning logs

 

[Gareth J]

Depending on the length of pipe, the heating cost for a small amount of hot water may be exceeded by the cost of running cold water to waste. Water is not exactly a cheap commodity to waste.

I'd never actually considered that. While water here isn't mains, if you were on mains, with drainage, according to my back of the envelope calculation, heating a litre water, with gas, is a similar order of magnitude to the actual cost of the water. The water cost is likely actually higher.

That surprised me.

So yea, if you've a sink far from the cylinder, at very least running it to warm in a jug or bucket for watering plants or whatnot is sensible. If it's used a lot, you can get point if use heaters that will modulate/top up water temp, might be worth considering although the pay back times could be very long.

 

[puffernutter]

Here's an update! Firstly, thank you all a very useful and informative thread (most of the time ) As they say in Dragon's Den - here's where we are!

We can fit around 4kW on the main roof, fitting the garage is possible, but will need more metalwork (flat roof) and will need planning permission (as I'll be over 5kW) so not worth it at the moment.

Our "base" load is around 1.8 - 2.0kW/h, we burn around 65-68kW per day (4 adults and 10 dogs create a lot of washing) it has made me look at the spend and make a few tweaks. We think a battery will be worth it. I'm also looking at putting a storage heater in the "dog room" to replace the use of the electric underfloor heating (which is mainly on at night) and charge through the day. We also have an electric immersion heater, so lots of use any excess.

Our current rate was fixed last August at 18p/kWh (just got in before it went crazy). So the back appears poor at the moment, but in August 23 when it will more than double, the payback looks better! We have no plans to move - some of you have seen my workshop, no chance of that moving anytime soon, and the house can be used/adapted as we get older.

The cost we expect to be around £12k for fitment and battery with a 10 year no-quibble warranty - it just gest replaced and they cover all the cost of replacement and argue with the manufacture if needed!

I may look at a "self install" on the garage/workshop later - I can make the frames and no scaffolding for access! See how it goes with the house.

I'll keep you informed of developments

Peter

 

[addjunkie]

The cost we expect to be around £12k for fitment and battery with a 10 year no-quibble warranty - it just gest replaced and they cover all the cost of replacement and argue with the manufacture if needed!

So by a that I make the battery bit to be about 7k??

 

[puffernutter]

So by a that I make the battery bit to be about 7k??

We were quoted around £6k for the battery, the bloke is coming back with the detailed quote tomorrow (Thursday) so I'll know the detail then. If we buy the battery as part of the installation, VAT is 5% if we add it later VAT will be 20%, so that's around £900 to give you time to make up your mind if you need one or not! We do seem to have some spare capacity (even on dull days) so we think a battery will be worth it.

 

[puffernutter]

It came in at £11,500 fitted. 3.9kW with an 8kW battery.

We are having it fitted in April. 10yr no quibble warranty including all costs of access. They seem to have all the right certifications and have been around 20 years, so some confidence they'll be around in 10 years time!

We're using Sustain Heating and Renewables from Bristol.

 

[addjunkie]

For your flat roof you dont always need steel work, you can get shaped plastic boxes they sit in.

 

[puffernutter]

For your flat roof you dont always need steel work, you can get shaped plastic boxes they sit in.

Good to know, thanks - any links to what I should look for please?

 

[addjunkie]

Renusol Console+bucket for flat roof solar panel installation - Trusted supplier for over 10yrs – ITS Technologies

The Renusol Console+ provides an angle of 15 degrees. The Renusol Console+ assembly system is the ideal solution for installing PV modules on flat roofs

www.itstechnologies.shop

there are others too