Comments on: At What Point Will Small-Scale Solar Energy Storage Become Viable?

By: Steve

Steve — Thu, 31 Oct 2013 07:47:00 +0000

Solar Purchase Power Agreements are the best way of banding together as a community to provide for your own electric needs as far as I have researched at the moment. These can be done through large companies that can cash in on rebates/by back excess energy or can be formed by a group of individuals in a local network who have the upfront costs collectively to do it themselves.
http://www.epa.gov/greenpower/buygp/solarpower.htm

By: Bob_Wallace

Bob_Wallace — Wed, 16 Oct 2013 22:08:00 +0000

Marine deep discharge batteries are not good for frequently used storage. A better choice is “golf cart” batteries, they have much thicker lead plates and will last a lot longer.

Even better than that are the new Trojan T-105 RE batteries which have been designed for off-grid storage. They’re rated at 4,000 20% DoD cycles or 1,000 100% DoD cycles.

And there seems to be better stuff coming. The EOS Systems zinc-air battery is reported to be good for up to 10,000 100% DoD cycles and be much cheaper than lead acids.

All that said, staying hooked to the grid is a much better solution, IMO as someone who has been off the grid for over 20 years. Being hooked up allows one to use much cheaper wind power rather than storing solar and/or using a backup generator.

What might make the most sense is to have solar, enough storage to take one through the evening hours, then run off wind power through the night while recharging batteries for the morning until the Sun kicks in.

By: Doug

Doug — Wed, 16 Oct 2013 18:47:00 +0000

The author’s calculations sized for a massive storage system using very expensive Li-Ion batteries. If the objective is to be removed completely from the grid, a very large storage system will be needed for cloudy, winter days. If the home/business can still be connected to the grid, a “80% solution” storage system can be much smaller – and can use less expensive batteries, such as deep discharge marine batteries used on sailing vessels and RVs.

By: Chris Kreider

Chris Kreider — Sun, 13 Oct 2013 11:22:00 +0000

I don’t know about CT but my electricity costs have come down. The assumptions are always the same PV costs come down, Battery costs come down, electricity prices go up, and you have to replace your batteries. I like Will E’s comment because he introduces a different answer Solar Hot Water provides storage. What about Storage in a Supercapacitor rather than a battery. Unlimited cycle life. Not chemical so temperature doesn’t effect it.

By: Will E

Will E — Wed, 09 Oct 2013 20:18:00 +0000

energy storage is not a problem for solar.
heating, warm water with a electric heatpump is a way of storage.
and buy an electric car to store your own solar energy.
no more gas bills and no more heating or airco bills.
storage problem solved
and you make money with it

By: Matt

Matt — Wed, 09 Oct 2013 18:28:00 +0000

But I bet that is 100% of your electric use last year, not 100% when the sun was shining. So still allows a good size system.

By: james2martin

james2martin — Wed, 09 Oct 2013 16:42:00 +0000

Hi Ray. Thanks for pointing out the errors in my calculations. I thought the numbers looked a bit low!

As for limits on solar export, a few Australian states had similar limitations on solar power export to make sure that no one (such as a rich neighbor) would install a system just to make a profit, and that systems were only used for saving money on power bills. Makes sense to me. But I also agree with SecularAnimist’s sentiment that there should be a way for small-scale system owners to band together and sell their electricity as a sort of distributed, ‘people’s power plant’. I’m sure it’s only a matter of time before that happens.

By: SecularAnimist

SecularAnimist — Wed, 09 Oct 2013 15:17:00 +0000

As far as I’m concerned, the more of us “neighbors” who can put up enough PV to “make money as a small utility”, the better. I would much rather pay my neighbors for whatever electricity I need from the grid instead of paying some big corporate coal-fired utility.

By: Ray Furse

Ray Furse — Wed, 09 Oct 2013 11:59:00 +0000

Hi James,

It’s an interesting question so let me give you the right numbers. In CT the rebate (from CEFIA) would be $9433 for a a 95.% efficient 7 kW system costing $28,000. Out-of-pocket to customer is $18,567, less 30% tax credit (not 32% and comes AFTER rebate in CT) so final system cost is $12,997, meaning payback is slower.

BUT, most importantly, rebates in CT are not given for any installed watts beyond what are needed to produce 100% of historical (previous year’s) usage, a disincentive to build big systems for sellback. This may sound counterintuitive but most people would not like to see their ratepayer funds used by a wealthy neighbor to build an oversized system to make money as a small utility.

Best,
Ray Furse
Litchfield Hills Solar