Delivered Kwhs from Solar Thermal

[tomhitchman]

I have a consultant coming around next week to look at the practicalities of Solar thermal.

Nowhere am I finding any data on delivered kwhs for a given size, location, and orientation. All I ever see is that it provides around 60-70% of hot water needs for the year.

Anybody got some real data or a calculator somewhere that will give an indication of these things?

I am in London with a south facing roof (give or take 10 degrees) and the tank would be around 40 foot beneath the roof.

many thanks

Tom

[adam2]

I dont think that you will be able to obatain any such figure.

Solar thermal collectors vary widely in efficiency, not just according to the design, but also according to the ambient temperature, the temperature of the water being heated, the water flow rate, and the wind speed.
All the above factors vary not only from one installation to another, but also from one minute to the next.

I would suggest chosing a system that can be readily expanded in the event that the output is initialy insufficient.

Remember that reputable suppliers will assume best case conditions, and disreputable firms may outright lie!

[IanG]

My view is if you've got a south facing roof you should stick PV on it.

You should look at either ground or air source heat pumps for space and water heating.

Solar thermal won't do 100% and it certainly won't do 100% this time of year, so you'll need an additional source of water heating. So why not invest in a technology that does 100%?

[RenewableCandy]

There are some building services benchmarks (BSRIA Guide BG1/2008 - The Illustrated Guide to Renewable Technologies) which give 454 kWh per m2 per year for flat plate and 550 kWh per m2 per year for tubes, assuming they're optimally placed. For solar PV the figure is 150 kWh per m2 per year (15% efficiency), and the m2 costs about twice as much.

But what really makes a difference is insulating the pipes, and the tank, and the timing of your hot water demand.

[IanG]

plus asset life.

No moving parts in PV - Panels warranted for 25 years
Inverters will be changed before then though.

costs about twice as much

I install Sharp PV at £3k per kWp after taking into account grant. EG 2kWp system will cost approx £6k.

[tomhitchman]

Thanks for all the replies...

In the end it was concluded that we could fit both PV 1.3kwp and solar thermal so depending on the consevation area rules etc then will have both and see how we go.

The PV was rated at 1100kwhs a year in the initial survey (is that realistic IanG?) so could net cover my usage per year which will be around 1030 to end of december.

Would be interested to find out how plausible/doable it would be to measure the kwhs delivered to the hot water tank but imagine this is quite difficult.

[IanG]

Tom,

I put 1.3 in the modeling tool, simple version - not taking into account panels / inverter.

Model output here

Who are you using out of interest?

[RenewableCandy]

I install Sharp PV at £3k per kWp after taking into account grant. EG 2kWp system will cost approx £6k.

Bargain!

How easy is it to get the grant these days? Last thing I remember reading that there were people hovering over their internet connections at 1 minute past midnight on the first day of the month and even they were sometimes disappointed...

[IanG]

the days of the 50% grant are long gone....

The max is £2,500.... but at least you'll get it with out having to wait up

[sjaglin]

I have a consultant coming around next week to look at the practicalities of Solar thermal.

Nowhere am I finding any data on delivered kwhs for a given size, location, and orientation. All I ever see is that it provides around 60-70% of hot water needs for the year.

Anybody got some real data or a calculator somewhere that will give an indication of these things?

I am in London with a south facing roof (give or take 10 degrees) and the tank would be around 40 foot beneath the roof.

many thanks

Tom

There are several tools you can use, solarmaster is one, designed for solar hot water:

Here is a brief description

Stef

[tomhitchman]

I recently got an email from Good Energy who are attempting to start a Heat Rocs scheme whereby those included who have solar thermal at home will be able to get paid 4.5p kwh of heat generated given by an estimate of the production over the year.

The details are quite sketchy at the moment here is an excerpt from the email :

Based on some very basic information & using our simple methodology, we believe that we can ‘deem’ your generators’ expected annual output without metering it at all! We’ll credit you with 4.5p for every kWh generated.

They are naming the scheme the Renewable Heat Incentive

If I have any more details I will update this thread.