Originally Posted by Cobb
Is the break even point calculated or guestimated?
It's a bit of both.
It is calculated. But it makes certain assumptions ( guesses ) about the future weather conditions and such. Although those future weather predictions are based on past historical trends, and they are a bit on the overly conservative side, the future is always a bit of a guess.
I know some of the financials , but not all of them.
The final financial deal was done behind closed doors between the owner of our company and the owner of the solar installations company.
I know historically ( sense 2009 ) the company had paid on average around ~$0.155 per kwh for grid electric.... highs up to $0.18 and lows down to $0.14 ... the $/kwh rate charged per month varies month to month.
I know the RI Utility company would not let them go over 495kw of AC output. The SunnyCentral inverter had to be programmed to never ( even under ideal conditions ) allow more than 495kw AC to be output from the system. At one point in the system options 698kw system was proposed ( Utility grid flat out rejected that proposal ).
I know they had tried for over a year to get into the RI Utility Grid's system for getting paid a 'green' rate for the kwh the Solar system produced. Those that get that can get up to like $0.28 per kwh they produce , while only buying what they need for regular ~$0.14 per kwh rates. That would have accelerated the whole thing allot. But the utility company kept fighting them, backing out of contracts, violating RI state policy etc ... and unfortunately... in RI if the Utility wants to get out of something the whole State Legislature passed all they has to do is get the majority of those sitting on the oversight comity to agree. Which is crap, but oh well.
Anyway.... so after a lot of fighting with the utility grid they just chose a straight net metering agreement which had less options for the utility grid to fight them on ... but it means it's a 1 for 1 even trade ... no additional 'green' power benefit from the utility company.
Sense they weren't getting additional $ from the utility company the company is able to sell renewable energy credits to other companies who want to ... at least on paper ... reduce their carbon foot print ... even if they aren't actually reducing their carbon foot print.... of course the prices for renewable energy credits vary also... they make an estimate (based on historical trends) used in their calculations , but prices change... future is not set and known... I've seen renewable energy credits vary from as low as $3/MWH to as much as $680/MWH.... AFAIK
RECs are only sold in 1MWH units. although it is yearly production.... so a home system that produced 1MWH over a year could sell them as well ... in addition to having a lower electric bill.
A conservative estimate would put the average yearly output over the 25 year warranty period as ~572MWH at just $0.15 per kwh ... that's over $2.1 Million in direct conservative electrical savings ... as electrical rates increase over the next 25 years this savings increases with them ... then on top of that there is also a tax right off for depreciation which is additional $ back you would have otherwise had to pay for taxes if you didn't have such a system to depreciate ... then there is the other $ back for the selling of the renewable energy credits.
Even without the additional 'green' selling of the kwh themselves to the grid ... it isn't too hard at all for the system to pay for itself.
I know initially early on around ~2 years ago the first installer numbers were around ~$2.80 per watt ... I know it was reduced to less than that in the end ... but I do not know by exactly how much to exactly what finial price.
December will be the lowest expected output month ... historically the lowest solar input for this location ... the 495 kw system might only do around ~30MWH for an average December ... of course that will fluctuate ... with some years doing better than average and other doing less.... and July will be the highest output.... +/- normal weather fluctuations.
Originally Posted by Cobb
This year Id like to try something with steam, a steam engine and an alternator with a gti. Im sure it wont break even like solar will in general, but it would be a neat hobby to have a solar powered generator.
definitely neat ... and I wouldn't rule out the potential to break even... it will of course depend completely on the details of costs, design, etc .... but solar heat collectors convert much higher % of the solar light energy to heat than PV convert the light energy to electricity... some solar to heat systems are over 80% light to heat efficient.
So First I would use the heat as heat for hot air and hot water... that's the biggest bang for the buck.
Then second if you have surplus solar heat collected ... If you're careful you could reasonably get up to ~30% stream ( heat engine ) efficiency from heat to mechanical shaft power ... a good generator can do over 90% from that mechanical to electrical ... and you are reasonably in the range of around ~21% sun light to electrical output.... so from an energy efficiency point of view ... it might be competitive.... just a question on what it will cost you ... and what kind of performance you can get for that $ investment.