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Neighborhood Battery/Water Heater

An efficient solution to the solar dilemna
  (+2, -1)
(+2, -1)
  [vote for,

Solar power only generates power during the day. At night, either fossil fuels or battery power must be used to keep things going.

Taking solar energy and storing it in a battery is never perfect, some energy will not be transferred to the battery and instead lost as heat. This idea is to use the waste heat to pre-heat water destined to enter a home's own hot water heater. There'd be a little extra plumbing but only on a local scale.

Ideally the battery needs to be large enough to the neighborhood over 48 hours without recharging, but making it through the night is better than nothing. A fixed central battery rather than a battery in every home means that a battery with higher maintenance needs can be used, rather than an idiot-proof room temperature battery.

For example, one current bettery technology is NiCd, which of course has special recycling needs and is toxic. There are at least two versions of NiCd battery: the idiot proof fully sealed consumer device, which unfortunately is only recycled 20% of the time, or the vented industrial kind, which currently boasts a recycle rate of 80%. Whatever technology is used, the target is the lowest cost for the total lifecycle, including recycling costs.

Madai, Mar 13 2013

it will probably mean less waste http://pubs.usgs.go...c/c1196o/c1196o.pdf
[Madai, Mar 13 2013]

A Solar Grand Plan http://web.chem.ucs...olar_grand_plan.pdf
a Jan 2007 SciAm article, mentioned in ano. [CraigD, Mar 13 2013]

Clean and environmentally friendly batteries made exactly for this purpose http://www.aquionenergy.com
High volume production ready in 3rd quarter of 2014 [pashute, Mar 14 2013]


       Well, let's work the numbers:   

       The average household (at least in the US) goes through about 958 kWhrs/month. In your 48hr period, you're looking at 64kWhrs. Let's say this neighborhood is a little gathering of.... 20 houses. So your 48hr period will need a battery packing about 1280kWhrs, or 1344kWhrs. Because let's face it, the inverter is going to loose 5%.   

       NiCd gets about 0.06kWhrs per kg. So, we're looking at a battery weighing 22352kg.   

       In terms of cost, lead-acid runs about $150 per kWhr, Li-ion about $400. I can't find it easily, but like everything NiCd I'd expect it to fall between the two. So, let's say $200 per kW hr installed. Which is going to make your battery $266800.   

       NiCd has memory, and also is done after about 2000 cycles. So we're looking at a 5 year replacement cycle costing $2670 for the battery per year.   

       Grid electricity is about $0.12/kWhr. About $1370 per year for the equivalent household.   

       So about two fold, just for the battery. Not including solar/wind/backup.... infrastructure like the chargers and inverters. Now, if this neighborhood lived near a mountain, and there were lakes, pumped storage would be the way to go.
bs0u0155, Mar 13 2013

       not to mention 22,000 kg of cadmium-contaminated waste to get rid of every 5 years. If 1% of US households went this way, 1.14 x10^6*22,000 = about 5 million tonnes per year.
bs0u0155, Mar 13 2013

       I heard an interview on NPR about a company that was building a battery for this exact purpose. Being NPR the interviewer asked exactly /zero/ technical questions about it, so I don't know how it was supposed to work.
DIYMatt, Mar 13 2013

       the 2000 cycle lifespan is based on a sealed cell.   

       with professional management/fixed location, the battery can use vented cell technology. 20+ year lifespan.   

       Also, the materials can be recycled. The neighborhood model should insure that the cadmium DOES get recycled, rather than accidentally thrown away by a careless consumer with a AA NiCd battery.   

       This is proven out in statistics: even now 80% of industrial batteries are recycled, 20% of consumer batteries are.   

       Cadmium losses when actually recycled are 0.1%, the bigger problem is all the consumer cadmium not being recycled at all.
Madai, Mar 13 2013

       The solar power at night problem is an old one, and while not successfully solved in a commercially competitive sense, has many well-to-over-baked solutions.   

       A bunch of experts published a big article in Jan 2008 Scientific American (see link) that proposed storing photovoltaic energy overnight as compressed air in big underground caverns at powerplants next to big consumers (cities). This design has not, to be best of my ability, had any large-scale prototypes.   

       Solar updraft towers utilize a design where sunlight is converted to heat, moving air by convection to drive air turbines to generate electricity. These can be managed – “throttled” – to generate continuously, night and day, matching day and night demand. Several large ones have been in operation for some time, notably in Spain and Australia. The design’s drawback is that it needs lots of intense direct sunlight and surface area.   

       Another design is pumped-storage hydroelectricity, where electric power from any source is stored by raising water. It has the drawback of lower efficiency, because water loses more energy to turbulence than air.   

       Flywheel energy storage is another old one design. It’s drawback is low energy density, requiring huge vacuum chambers and flywheels to substantial amounts of energy, so has found a niche mostly in meeting short-duration electric generation needs, such as power-failure backup and grid load- leveling.   

       Chemical battery storage are usually a design of last resorts, for reasons of the drawbacks previously annotated.
CraigD, Mar 13 2013

       If the battery had a 1.5V output, it could also be used to provide power for the neighbourhood watch.
MaxwellBuchanan, Mar 13 2013

       //Solar updraft towers ...in Australia// There was a lot of noise and promotion about this project - not really as an efficient way to economically produce power but as a 'demonstration project'. Nothing ever happened as far as I know.
AusCan531, Mar 14 2013

       So... the "idea" part is _using_ the waste heat created when the battery is charging. Hot water heating is typically 12-21% of total energy needs depending on climate.   

       I suppose I shouldn't have bothered talking NiCad. The real fix to go with whatever delivers the lowest total yearly cost per installed kWh, with recycling needs folded in.
Madai, Mar 14 2013

       The first plus here is mine! Sorry, but didn't have the time to find and post the link till now. Anyway the idea is great if you can use an environmentally friendly and safe battery. Which is exactly what Aquion developed.
pashute, Mar 14 2013

       [+] for spelling "dilemna".   

       Per the idea, well it sounds like it may have some strong points, but you might want to proofread that third paragraph a bit for content.   

       Where's your "solar power" coming from: individual rooftop collectors ? in which case the residual radiation (70%) might as well be used to preheat water, as well as battery charge/discharge losses.
FlyingToaster, Mar 14 2013

       Okay I did a substantial re-write.   

       to answer the question and talk about residual radiation:   

       Yes, the solar panels will be on the roof, mostly.   

       I suppose if solar heating can be done easily enough, the panels could be dual purpose, getting both electical and heat energy.   

       I was hoping that having a central battery and central heat exchanger would confer advantages over a single home system. But perhaps a large enough array on a single home could provide suplus electricity AND surplus hot water too.   

       I wish there was some way to efficiently, locally, allocate all or most of the surpluses.
Madai, Mar 18 2013

       AFAIK, commercial PV isn't particularly viable, however, those solar towers, with the molten salt and the parabolic mirrors are much more up to scratch. Perhaps, a neighbourhood version of this could be built? Hell, if you're going to have a big tower, why not life in the bottom 2/3rds of it? Then you've got lots of high grade heat to make steam out of, and low grade heat (from the turbine condenser) for your washing machine and so forth. No need for pesky batteries, the whole thing could be a water tower as well, excess energy could be used to pump water up and recover it on the way down.
bs0u0155, Mar 19 2013


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