[Greenbuilding] Swedish solar-heated village

Wed Nov 25 16:37:11 CST 2015

Growing up in Germany we were exhorted to, for instance, *not wash clothes
on Mondays* for purposes of load balancing. Traditionally German housewives
did the laundry on Monday and German washing machines heat their own water,
thus the spike the grid operators were trying to flatten. I don't see why
we couldn't revisit this kind of communication aimed at shifting demand.
Dishwashers gthere were/still are supposed to be run at night, etc.

On Wed, Nov 25, 2015 at 12:11 PM, Dan Johnson <danjoh99 at gmail.com> wrote:

> It's great to see Nick Pine back on this list. I want to point out for
> discussion that the electrical grid has virtually no storage! The grid
> follows load and must be balanced nearly instantaneously with dispatchable
> generation.
>
> Contributing PV energy to the grid is often part of the problem, because
> renewables often need to be curtailed when production exceeds demand. Grid
> operators can't taper down the baseload generators every time the wind
> picks up. The California ISO site has a lot of current information and I've
> found it a great place to learn about the electrical grid. And this is one
> of the most progressive operators in terms of their renewables and storage
> mandates from the State. http://www.caiso.com/Pages/default.aspx
>
> Bringing this back to solar storage in winter (in California, for
> example), when I do morning warm-up or heat during a cloudy day using my
> electric heat-pump, the electric grid is running natural-gas-fired
> generators at an emissions rate that is dirtier than average. This is
> because renewables are generally not online during these periods. Check out
> this net-demand chart from Cal ISO: the morning peak of the green line is
> all fossil fuel, before solar comes online.
> http://content.caiso.com/outlook/SP/duck.gif. There may be less emissions
> and less fuel burned if I just burned the natural gas at my house with a
> condensing appliance, as a backup to my passive systems, using no storage.
> The chemical bonds in the natural gas provide the storage. :-)
>
> Any net surplus of PV from my house would occur when I don't need it to
> power a heat-pump or A/C: these are periods when likely other houses don't
> need it either. Net consumers would be commercial buildings, hospitals, and
> other process loads on the grid. In one scenario, we can ramp-down the
> fossil generators during these periods, so **here is where we can argue
> that the homeowner's PV could be considered a carbon offset**---but no more
> real than Terrapass. http://www.terrapass.com/. In another scenario, the
> added power from renewables just lets us bring more loads online---total
> load and demand grow over time! This is the opposite of what we wanted.
>
> Returning to grid-scale storage: it seems this is science fiction, like
> clean coal. Euan Mearns has some great analysis of experimental pumped
> hydro schemes in the Canary Islands.
> http://euanmearns.com/el-hierro-another-model-for-a-sustainable-energy-future/.
> California conducted a workshop in Jan 2014 on pumped storage and many
> presentations from it are here:
> http://www.cpuc.ca.gov/PUC/energy/electric/Technical_Workshop_Understanding_Current_State_of_Pumped_Storage.htm.
> If 300 high reservoirs were built along the coast, using the ocean as the
> low reservoir, the grid could get 572 GWh of storage, almost 1 day of
> storage for California!
> http://www.cpuc.ca.gov/NR/rdonlyres/1521FE3B-2FB5-4A6A-A93B-45125D6EF895/0/Barnhart20140116CPUCPHSWorkshop.pdf
>
> Best,
> Dan Johnson
> Albany, CA
>
> On Tue, Nov 17, 2015 at 12:06 PM, Nick Pine <nick_pine at verizon.net> wrote:
>
>> Kimmo writes:
>>
>> I’m an entrepreneur that is doing research the possibility to use some
>>> architecture ideas to heat houses in Sweden similar
>>>
>> to what Soldiers Grove did back in 1979. We will of-course try to
>> modernise the design but the basic concepts are the same
>> with the “solar attic”.
>>
>> Soldier’s Grove attics required moving warm air down to the lower part of
>> the building using fans or blowers and a motorized damper, and it’s hard to
>> store solar heat from warm air. I figure cloudy days are like coin flips,
>> so a building that can store enough heat for 1 cloudy day can be at most
>> 50% solar heated, with a possible max 1-2^-N solar heating fraction if it
>> can store enough solar heat for N cloudy days in a row, eg 1-2^-5 = 0.97
>> with 5 days of storage. Most of the SG buildings were only 50% solar
>> heated. Why stop there?
>>
>> It seems to me that collecting enough heat to warm a building on an
>> average day would be simpler with some passive solar heaters built into the
>> south wall, eg
>> http://www.builditsolar.com/Projects/SpaceHeating/solar_barn_project.htm
>>
>> Where I live near Philadelphia, PA, 1000 Btu/ft^2 of sun falls on a south
>> wall on an average 30 F January day, so a 4 foot x 8 foot vertical south
>> air heater with US R2 twinwall polycarbonate glazing with 80% solar
>> transmission would gain 0.8x32ft^2x1000 = 25.6K Btu/day. With a 70 F
>> building and a T (F) exit air heater temp and a (70+T)/2 average air temp
>> inside the heater and a 6-hour solar collection day, the heater would lose
>> about 6h((70+T)/2-30)32ft^2/R2 = 48T+480 Btu/day. With a constant C cfm
>> airflow, the collector would provide 6C(T-70) Btu/day of heat to the
>> building... 2 1 ft^2 vents with one-way plastic film flappers and an H = 8
>> foot height difference would make C = 16.6x1ft^2sqrt(8'(T+70)/2-70)) =
>> 33.2sqrt(T-70) cfm, and 25.6K = 48T + 480 + 200(T-70)^1.5 makes 543 = T +
>> 4.15(T-70)^1.5, ie T = 70+((543-T)/4.15)^(2/3). Plugging in T = 100 on the
>> right makes T = 92.4 on the left, then 92.7, then 92.7, with C = 158 cfm
>> and a 6x158(92.7-70) = 21.5K Btu/day heat gain for the building, which
>> might have just enough thermal mass and insulation and airtightness to cool
>> from 70 to 60 F by dawn... 60 = 30+(70-30)e^(-18h/RC) makes RC =
>> -18h/ln((60-30)/(70-30)) = 63 hours.
>>
>> And given the present low cost of PVs and inverters, we might heat the
>> building with Mitsubishi or Fujitsu mini-split heat pumps on cloudy days
>> (they work with an outdoor air temp down to minus 13 F), powered by PVs,
>> using the electrical grid for storage instead of a 5000 gallon hot water
>> tank. How many peak watts of PV would be required for space heating alone,
>> with a COP of 3? A simulation using hourly EPW weather data could help
>> estimate this.
>> http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data3.cfm/region=6_europe_wmo_region_6/country=SWE/cname=Sweden
>>
>> Then again, a solar village could have passive solar air heaters on each
>> house and a large common underground heat storage tank with a geodesic
>> transparent roof and a simple drainback hydronic collector on top of a
>> floating insulated cover under the roof.
>>
>> Nick
>>
>>
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>
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