• Dec 26th 2009 at 8:31AM
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With the various tax incentives available, there is an increasing interest among homeowners in incorporating some sort of renewable energy system to help get partially or completely off the grid. The problem is that unless you live adjacent to a hot spring that you can use for geothermal, the other primary sources are wind and solar power. Both wind and solar are great, except for their somewhat intermittent performance. For that reason, you need some kind of battery buffer system to store energy when the sun is shining or the air is in motion so that you can use it at night or when it's calm.

Depleted electric vehicle batteries have been discussed as a good source for these buffers, but at the moment there isn't a readily available supply. Panasonic plans to step up to the plate and produce a lithium ion battery pack specifically for home storage use beginning in 2011. The home storage battery was initially developed by Sanyo, but Panasonic recently acquired a controlling interest in that company. They are now working together to bring the system to market and will make further announcements in the first half of 2010.

[Source: PhysOrg]

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    • 1 Second Ago
      • 5 Years Ago
      You forgot microhydro -- it's much easier to tap a stream running downhill across your property than to use residential-sized geothermal to generate electricity:

      Of course, small hydroelectric installations come with their own set of gotchas and subtleties, and most people don't have such a resource in their back yard... But I'd put it, along with solar and wind as the big-3 in small-scale renewable energy.

      Using a geothermal heat pump to heat your house is different deal. It's very useful and a great way to cut energy costs. But it's hard to make electricity with that kind of geothermal loops -- unless you live near a hot spring or in Iceland or something.

      As always, Home Power Magazine has lots of good information about this kind of thing:

      Batteries are a big deal with renewable energy systems, and I've been wondering when the apparent-advances in battery technology required to get electric cars this far will filter over to renewable energy. It would be even better if I could afford such a battery!
      • 5 Years Ago
      I have a hard time understanding why these incredibly expensive batteries are somehow better than high quality and much cheaper sealed AGM lead acid batteries. I installed off-grid systems for years and lived in my own off-grid home with a good sized AGM battery bank. The limitation for vehicles that makes Li-ion practical for cars is size and weight, neither of which is an issue in a home. Plus the no-maintenance of sealed batteries beats the hell out of flooded cell batteries.

      This seems silly and strikes me as just playing on the ignorance of the public by throwing some "new technology" at them that they've now heard about with all the talk about EVs.

      I'm guessing these are designed for use in grid-tied homes where the only need is to get through a couple of hours of power outage but the reality of grid-tied homes is they are nowhere near as efficient with power usage as an off-grid home and the need will be there for high-amperage 220v power use and that will still require a pretty big battery, even for a couple of hours because the discharge rate can't be too high.

      Give me a set of quality AGMs anytime and I'll buy a Prius with the money I save.
      Lookup MGTOW
      • 5 Years Ago
      Waitaminute. Doesn't Geothermal add net heat to the troposphere?
      • 8 Months Ago
      Ok, I have found some better info which makes more sense of what Panasonic is up to:
      'Panasonic continues to work to increase output of direct methanol fuel cells, capitalizing on the above technologies that have achieved downsizing and high durability. As a next step, it plans to develop a portable generator with an average output of 100 W that will be much more compact than engine-generators. Combining the fuel cell generator with its high-capacity lithium-ion battery module, Panasonic aims to bring to market an outdoor power source that integrates energy-creation and energy-storage functions.'


      A weeks power supply stored at 100Watts is down to believable figures - 16.8kwh of storage.

      I would have thought the US military would take all that Panasonic can make of these little babies without considering other markets.
      • 5 Years Ago
      You don't need a hot spring to use geothermal energy, ground temperature is much more stable then above ground, anyone with enough land can run pipes and use geothermal power to assist heat in the winter
        • 8 Months Ago
        The new CO2 air source heat pumps will do the same job as geothermal heat pumps at a fraction of the cost.
        They are fine for sub-zero temperatures and multiply the electric power for space heating by 2.5-4 times depending on the layout and if it is a new install, where you can lay underfloor pipes which are the most suitable or adapting an existing build where you need to oversize the radiators as the water is rather lower temperature than is conventional.
        They can also be used with air heating and cooling instead of water central heating, but I know less about this as it is not common here in the UK
        • 8 Months Ago
        Chris M:
        If you are building a ground source heat pump then the pipe thickness is of more concern - but that is precisely my point, you don't need to now.
        Whatever the other comparisons between using CO2 or other refrigerants, the big difference is that the CO2 air source pumps operate very comfortably and with good efficiency to temperatures way, way below zero.
        Older heat pumps were fine for maritime climates such as the UK, where the temperature rarely stays below zero for long.
        CO2 air source heat pumps are fine for very extreme climates such as Alberta or Michegan.
        Sure, you may get a little more efficiency from round source, but on a cost/performance basis there is no comparison.
        You have a resonable sized unit attatched to the outside of your house, you don't have to dig up the grounds or install underground loops etc:

        Don't take my word for it, you can price up off the shelf systems right now - see the previous links I gave.
        • 8 Months Ago
        David Martin: While CO2 can and has been used as a refrigerant, it requires much higher pressures than other refrigerants, thus requiring thicker gage piping which increases costs and reduces efficiency. Ammonia, Freons, or Butane are much cheaper and more efficient choices for refrigeration or heat pump usage.

        The advantage of ground source heat pumps is that underground the temperatures are usually higher than air temperatures when heat is needed most. That, in turn, leads to higher thermodynamic efficiency. The main concern with ground source heat pumps is that all the heat taken from the ground must be replaced over a years time, otherwise the ground will get colder and colder and the efficiency advantage would be lost. Fortunately, hot summer weather is a perfect opportunity to "rewarm" the ground source and prepare it for the coming winter.
      • 5 Years Ago
      What I like about batteries to stock your own green energy VS putting it into the grid is that it acts as an incentive to consume less :
      If I had produced my very own green electricity and could use it, each kwh would me more "precious", and I would try to level my consumption to what I have produced.
      It's a bit like when you build something yourself VS buying it from the store : you get the notion of how hard it is to obtain it, so you tend to value the object more, and here with the added pride of being environmentally friendly.
      That's how I would feel anyway...
      • 5 Years Ago
      If I had money to invest in power buffer batteries, it wouldn't be in lithium ion, but vanadium redux flow.
        • 8 Months Ago
        Yeah, me too.
        I am not quite sure what they consider a 'week's power' in Japan, but in Western terms that would involve at least a flow of 1kw, so you would need 168kwh of batteries!
        Even at $250kwh, that is around $42k, and AFIAK no-one has got anywhere near that price.
        So this is either some sort of technological demonstration, or they are looking at a very restricted power supply.
        This is an interesting one though, and at minimum means that a handy stationary battery pack system has now been built.
      • 5 Years Ago
      David, great link. I especially like the second part about the fuel cell that if used 8 hours per day the 5000 hour fuel cell would die after 625 days or a little over a year-and-a-half. That's not much better than lead acid batteries as far as I can tell (many have a 500 charge/discharge cycle lifetime or more).

      Meanwhile, battery technology improvements continue on pace, "2.9 Ah (current) 3.4 Ah (FY 2012) 4.0Ah (FY 2013)" from the above link - a 38% capacity improvement in the next 3 years.
        • 8 Months Ago
        David, I only mentioned the improvements to the Lithium-Ion batteries as an example of the pace of advancement in battery technology. The small cells discussed in the link are similar to the ones used in the Tesla so they definitely do have potential for EV use.

        Contrast that with the glacial pace of advancement in fuel cell technology.

        Fuel cells may actually be the best technology during the next 10 years for police, ambulance, fire trucks or long haul truckers (the so-called heavy duty vehicles) but they are definitely the most expensive. I am just not sure that it would be worth the expense to convert them to fuel cells when compared to just converting those vehicles to LPG/natural gas. Natural gas vehicles reduce CO2 by 40% and other pollutants by 90% over gasoline. It is much cheaper to convert a "gas station" to natural gas than to service fuel cell vehicles. And it is domestic.

        BEV is the only option for LDV (light duty vehicle) use today and into the future. In 10 years battery technology will have improved and will be adequate for use in heavy duty vehicles as well.
        • 8 Months Ago
        Warren Buffet invested in BYD for just this purpose.

        When MidAmerican bought its BYD stake, the media jumped to the conclusion that Mr. Buffett was placing a bet on electric cars. Cannily, Mr. Buffett and MidAmerican executives made no effort to dispel this impression. But all evidence suggests their interests lay elsewhere. MidAmerican Energy Holdings runs power grids that generate more energy from renewable sources than any major American utility. MidAmerican's subsidiary in Oregon, PacifiCorp, recently erected a building the size of ten 40-foot storage containers that houses BYD batteries. Those batteries are being tested for the storage of wind-generated energy. BYD's real contribution to Mr. Buffett's portfolio will probably be low-cost, relatively low-tech batteries that store wind and solar power for use on days that are breezeless and cloudy.

        • 8 Months Ago
        Tom, for most uses you do not run 24hours a day.
        This is in the right ball-park for use in cars, as though as I emphasised a f/c for a laptop is very different to a car battery.
        At 2 hours a day, you would get around 7 years use, which is far more than has been typical previously, and is a good starting point as presumably it can be further improved.
        • 8 Months Ago
        I have just re-read the article, and clearly since they have based their durability estimates on 8 hour runs of intermittent use, we should be careful of trying to generalise to other use - they are looking at it for running a laptop etc, after all.
        What we can safely say is that this appears to be much better than what was previously possible, and represents good progress.
      • 5 Years Ago
      I like the idea of coupling a solar hot water system with a geothermal heat pump so that in summer you heat your hot water with the heat pump via rooftop heat, and then pump the remaining heat into the ground for pulling it back out months later to heat your house. To make this even more efficient you could use an old swimming pool, line it with insulation, fill it with earth, cap it off, and you have a huge thermal reservoir.
        • 8 Months Ago
        Want to use an old swimming pool for heat storage? Fill it with water and put on an insulating cover, don't "fill it with dirt". Water has the highest thermal mass of any known liquid, much higher than soil or rocks, and for each degree of temperature increase water stores more BTUs, by volume or by weigh. Water also has better thermal conductivity which makes it easier to move heat in or out. It is also easier to pump water around than to try and pump dirt.
        • 8 Months Ago
        Thanks for the oil drum link, it is very informative. I think a range of options are best, with each person's solution best tailored to their particular situation. In North America there is not enough attention paid to this, everyone just throws in a natural gas furnace because they are the cheapest to install. There is a huge focus on building houses here (that is now what keeps the US economy afloat, with all its manufacturing having moved overseas. In Canada we develop fossil fuels to supply the US and bring in more and more people to participate in this growing but unsustainable economy -- a recipe for economic disaster over the next few decades, but that's an aside.)

        There is a mentality of getting the houses built for as little money as possible and then spinning them off in the speculative real estate market as quickly as possible. For this reason I would never buy a brand new house here unless I was directing the construction because you don't see the problems until a few years down the road.

        So while overall, the long term financials of installing a heat pump are in their favour, the increased capital costs of installing one will dissuade many builders from using them, because they simply aren't in it for the 5 year financial situation. They are in it to make a quick profit.

        This is where I believe governments should be more proactive. One of the things they could do is have inspectors come out during construction and certify that a house has been built to be properly insulated. This could be a selling feature of the house, it is easy for the buyer to understand. Maybe they already do something like this, I don't know. Another big thing they could do is provide low interest loans to home builders so that they can buy a heat pump at the same price as a natural gas furnace, and then pay it off over 5 years or so in monthly installments, which will work out to be the same as the savings in monthly heating bills. So then there is no upfront cost to the heat pump.

        The other problem is that few people even know what heat pumps are, there is a mentality of natural gas furnaces. Therefore, there isn't much pressure to change things.

        My mom won't be installing a heat pump on her property though. She uses a wood stove which is renewable and cheap, although it does produce pollution but in winter it's not that big of a problem. If we were to go for a heat pump we'd use the well. Maybe drill another well about 30 feet away and draw from it, take out the heat, then dump the water back into the drinking water well.
        • 8 Months Ago
        The Conservative opposition, who will likely come into power in the summer, are to introduce a system where you pick up a leaflet at a supermarket, and d they finance the installation of insulation or other equipment.
        The savings are split between the owner and the supermarket, with moeny off the energy bills right away, and even more once the capital is paid back.
        Private individuals do not usually lay out that much in capital to save a little every month, so it should be a help.
        This sort of measure originated in California, where they first started paying utilities to provide a service rather than according to how much power they sell.

        If you already have source of water such as a well, the economics are very different to having to build a ground loop.
        Whatever their merits or otherwise for transport, fuel cells running on natural gas are much more energy efficient for providing power in the house than generating electricity remotely, so if your mom is on the grid for gas do check out the prices.
        • 8 Months Ago
        Check out the price of ground source heat pumps and all the digging you need to do.
        Then check out the latest air source heat pumps and the prices - very reasonable.
        You really, really do not need to go to the expense of ground source heat pumps since they brought in the CO2 air source models.
        More here:

        Check out 'Here in Halifax's comments:
      • 5 Years Ago
      It's not just the battery - other components needed to interface batteries with the home's AC grid such as the inverter are pricey (and historically, inverters haven't proven very reliable)
      • 5 Years Ago
      I think these would face a very uphill battle against premium FLA batteries such as Surrette. With proper maintenance those batteries will last 20 years and more, is that possible with lithium batteries? Also, things like weight and size don't matter nearly as much for home based battery systems.
      • 5 Years Ago
      Great idea! Cost vs home backup generator?

      Then again, a generator can't be used power system for load-leveling or storing cheap evening power for daytime use.
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