Green solar panels? RHI buyers guide: solar thermal technology selection criteria. Here are our solar secrets!
Here is idea of some of the huge range of questions which people ask us at Solartwin when choosing solar water heating systems for subsidy such as RHI. We can ask but we can’t answer all of them! We hope this is useful!
Aesthetic considerations
- visual appearance – how will the solar panel look?
- do I want novelty or innovation from my solar panel
- does solar bring discomfort such as more cold showers?
- does solar bring hassle such as sudden breakdowns?
- does the solar installation bring hassle by taking a long time to fit?
- will I have to wait long for the solar installation?
- does the solar installation imply official hassle, authorisation or planning permission?
- will my friends and neighbours approve of my solar panel installation?
- is my solar technology from ethical suppliers?
- is solar intrinsically safe?
- can I cope with the solar controls?
- are the solar installers nice people?
- will it affect my home structurally?
Financial considerations
- will solar increase the value of my home?
- what solar buying incentives are in place to buy now?
- what does the solar installation cost? / per watt?
- can I get solar for free? If so, what are the drawbacks?
- how can I pay? Do you offer solar finance? Staged payments beforehand?
- total money saved per year (break down by heating fuel – electricity)
- What costs will go up each year? Insurance, electricity, average maintenance?
- What is the net benefit ie effect of savings minus costs?
- What if I factor in the cost of finance, say if I had taken the money out of an interest bearing account? How much do I gain or lose per year?
Energy considerations for solar panels
- What is the embodied energy of my solar installation? (The total life cycle energy used to make it.)
- Energy saved per year (heating fuel – electricity) Base line is the year before: real or simulated?
- Annual operational coefficient of perfomance (a ratio: energy in / net energy out)
- May I see two before and after solar Sankey (energy flow) diagrams of annual energy including parasitics?
- Look at all the various ratios such as solar fraction etc. (see comment below)
CO2 considerations for solar panels
- What is the embodied carbon? (The total life cycle carbon impact of making it.)
- CO2 saved per year (heating fuel or electricity)
- Annual operational coefficient of carbon perfomance (CO used / net CO2 saved)
- May I see two before and after Sankey type diagrams of CO2 including parasitics?
- Would choosing a PV pumped solar thermal system improve performance?
Time considerations relating to the above solar questions:
- How long to capital+operational +maintenance financial breakeven?
- How long to embodied+operational+maintenance energy breakeven?
- How long to embodied+operational+maintenance Carbon breakeven?
- What is its life expectancy? How does this compare with the above – with mine!?
- What % of its net money savings is spent paying back its initial cost+operational+maintenance money?
- What % of its net energy savings is spent paying back its embodied+operational+maintenance energy?
- What % of its net CO2 savings is spent paying back its embodied+operational+maintenance CO2?
How do these figures (where they are available!) compare with other:
- Financial investments (such as leaving the money in the bank)
- LIfestyle changes (such as walking to work)
- Energy saving measures (such as upgrading loft insulation)
- Microgeneration technologies (such as heat pumps)
Solar fraction is overrated by the solar water heating industry. Nice and simple, it is fast becoming a rock solid myth. I am concerned that minimising solar fraction is a very distorting objective. This is because you can simply achieve high solar fractions by giving the customer lots of cold showers when it is not sunny! Traditional twin coil cylinders installers can actually exacerbate the cold shower problem by only heating half the cylinder, rather than all of it. Solar fraction is a poor goal to pursue. Take a look at this video for example.
http://www.youtube.com/watch?v=J9v68zr213A
It only takes one minute if you start at minute 8 and end at minute 9
I produced this solar video because a plumbing trade body had cheekily attempted to tell the government grants gateway committee (MCS) that counting the nergy saved by giving the consumer more cold showers in a year could be treated as an energy benefit which was attributable to installing a solar panel! What fun!
The point is that ratios (or fractions like this) are subject to “gaming”. The solar fraction is about two figures of which the numerator is not being trimmed by the parasitic energy consumption of pumps etc, (when it should be) and the denomonator is being manipulated to be too low. Overstate the the numerator by ignoring parasitics and understating the denominator by making the customer endure more cold showers than before solar and you risk misleading them.
So the alternative? Well, Quantities of energy are better issues to look at.. Before and after is the comparison to make, including the fact that the electricity bills may rise while gas bills fall.
Minimising bought in energy (heating and electricity) compared to their original non solar consumption is a better measure of solar heating system effectiveness than solar fraction. If a solar simulator is being used to deliver the solar performance estimates then ideally the simulation should be rerun without solar and a comparison made. The consumer needs some online solar thermal simulators now.
I do hope this is an interesting contribution to the solar debate. Barry
