East/West Facing Solar Water Heating Panels

RenovationMan

Hi, I have a DPS Heatbank that was installed last year and connected to a new gas condensing boiler and wood burnign stove. The plan is to also add solar water heating to the mix (the bosses and coil are pre-installed in the Heat Bank) but cannot install the panels on my south facing roof because the house is listed and the roof is in partial shade from protected Beech trees.

The alternative is to install them on a single storey double garage at the rear of our house, but the problems with this are:

1. The roof pitches face East and West.
2. Our house is three stories (four including loft) and so whent he sun is lower in late autumn/winter/early spring, the roof is in shade.

The question I would therefore like to ask is whether anyone has experience of East/West facing installations and a general question about whether I am losing much by not having the panels working during early spring/winter/late autumn?

I guess what I need to know is, given the restrictions I have, whether the payback will be sufficient to justify the cost? Though part of the cost is already covered in as much as I already have the hot water storage in place.

Cheers in advance for all/any replies!

Cardew

RenovationMan wrote: »

I guess what I need to know is, given the restrictions I have, whether the payback will be sufficient to justify the cost? Though part of the cost is already covered in as much as I already have the hot water storage in place.

Cheers in advance for all/any replies!

Even with the most favourable South facing roof, solar thermal will never pay back the cost.

There are several threads on this, but around 1,000kWh pa is average. - £30 or so a year with a new gas boiler and nearly all produced in Summer.

So in money saving terms solar thermal is a joke.

The proposed Renewable Heat Initiative(RHI) may change this situation.

RenovationMan

I assume that it all depends on the cost of installation & mantenance Vs the cost of mains gas. I obviously need to keep down the equipment and installation costs to make it pay, and as I already have my thermal store, that a large component removed from the costs.

Thermal stores can store water at higher temperatures and in larger volumes than a standard cylinder, which means that more of the heat produced by solar can be stored. The insulation is also better on heat banks, so if I get a really sunny day, followed by a cloudy day, the water will still be warm from the previous day.

The heat bank also supplies hot water for my heating, so in late spring and early autumn, when we may need a bit of heating on a chilly day, solar could supply most of this too.

The final consideration is just how much gas prices may rise in the future now we are a net importer of gas. The more this goes up, the faster the payback.

Cardew

The problem is you produce most of the solar thermal energy during the summer when you don't need heating.

Certainly if you have enough panels you can have enough hot water in the summer for all your baths and showers, but you will get virtually no useful heat in the winter and probably less than the cost of running the pump.

Cardew

If you want an unbiased report on solar thermal read this Government sponsored trial.

Have you seen this exaustive trial of 8 systems carried out for the Dti at Cranfield? *

http://www.dti.gov.uk/files/file16826.pdf

*
For those not conversant with the units used!
For the 8 systems tested(evacuated Tube and Flat plate) the annual output ranged from 3440 MJ(megajoules) equal to 955kWh to 4,820MJ(1,339kWh)
However from that total had to be deducted the ‘parasitic’ energy to run the pump and electronics. This ranged between zero and 390MJ(108kWh) pa. This of course is daytime rate electricity.
The average for the 8 systems was just over 1,000kWh per year.

So 1,000kWh per year.

Look at the results for the output each month. When you need heating, solar thermal produces energy worth pennies.

RenovationMan

Cardew wrote: »

The problem is you produce most of the solar thermal energy during the summer when you don't need heating.

Certainly if you have enough panels you can have enough hot water in the summer for all your baths and showers, but you will get virtually no useful heat in the winter and probably less than the cost of running the pump.

I agree that I wouldnt need heating in summer, but thats why I mentioned using the heating during late spring and early autumn when it sometimes gets chilly and we often run the heating for an hour or so to warm the house through a little bit. As I have already said, due to the position of my house, we will get zero hot water in Early spring/winter/late autumn and so that wouldnt factor in my calculations.

RenovationMan

Cardew wrote: »

If you want an unbiased report on solar thermal read this Government sponsored trial.



So 1,000kWh per year.

Look at the results for the output each month. When you need heating, solar thermal produces energy worth pennies.

From what I have read, solar heating will supply all my water needs in summer and most of my needs in early autumn/late spring. Depending on my installation costs, which I have already mentioned should be reduced due to some components already in situ, there must be a payback within the 25 years of having the solar installed.

There is no 'one size fits all', so I cant see how anyone can categorically state that solar water heating never pays back, ever, in any circumstances. Especially given that we dont know what wholesale gas prices will be in even 5 years, let alone 10 or 15.

I would be interested in some 'real-world' examples of solar water heating from anyone who currently has it, especially those with E/W configurations.

Cardew

RenovationMan wrote: »

From what I have read, solar heating will supply all my water needs in summer and most of my needs in early autumn/late spring. Depending on my installation costs, which I have already mentioned should be reduced due to some components already in situ, there must be a payback within the 25 years of having the solar installed.

There is no 'one size fits all', so I cant see how anyone can categorically state that solar water heating never pays back, ever, in any circumstances. Especially given that we dont know what wholesale gas prices will be in even 5 years, let alone 10 or 15.

I would be interested in some 'real-world' examples of solar water heating from anyone who currently has it, especially those with E/W configurations.

If you get 1,000kWh per year that saves you £30 a year(and we will leave out the cost of running the pump and electronics at daytime rates)

How much do you think a solar system for your house will cost? £2000? 3000?

Invest the, say, £2000 in a long term building society and you will get 4% to 4.5% after tax so £80 to £90 interest compounded.

So how will the system ever pay you back.

Now talk about future repairs to the pump and electronics.

Read WHICH if you want some more information on the viability of solar thermal.

RenovationMan

LOL, do you work for British Gas?

Just joking. Thanks for your input, you have given me a lot to think about.

Cardew

This article must be correct - it is from the Daily Mail!!!!!!!

http://www.dailymail.co.uk/news/article-1274784/They-tell-solar-panels-eco-friendly-save-money-The-truth-They-dont-work-time-100-YEARS-pay-.html