[Greenbuilding] Swedish solar-heated village

Mon Nov 30 12:31:08 CST 2015

Thanks John for the Danish examples of district heating powered by
centralized solar-thermal. A few questions come to mind:

1. What is the installed and operating cost per BTU for this system, versus
the same solar-thermal panels on individual houses without the district
loop? Or compared to a Nick-Pine-style low-mass sunspace on each house---or
to Soldier's Grove, Wisconsin? It seems like this Danish system adds the
cost of the district loop, yet has all the same problems as distributed
solar heat.

2. Problems being primarily: there is no heat when the sun's not shining.
For this, Nick suggested a heat pump and PV panels, "using the grid for
storage". I pointed out that the grid has no storage, and the PVs are more
like a shady carbon offset scheme, so perhaps there is only "storage" in
the wishful abstract.

3. The Danish system solves the problem of
no-heat-when-the-sun's-not-shining using 4000m3 hot-water storage [8.8
million pounds of water], and by burning natural gas in a central boiler
and sending hot water through the district loop. This is not much different
than homeowners storing hot water and burning their own natural gas at each
house, is it? From the brochure linked here:
http://www.sonderborg-fjernvarme.dk/wp-content/uploads/2013/06/Solparken_folder_gb.pdf,
"The boiler plant is able to supplement the solar heating with up to 5
kilowatt [only 17 kBTU/hr? Something lost in translation]. The plant
consists of two boilers that run on ***CO2-neutral biofuel***" Magical
stuff. where do I buy some? Why don't we just replace ALL natural gas with
this? :-)

4. Compare the Danish scheme to PG&E in California, which burns NG at a
generator to make electricity (combined cycle claims 41-61% efficiency,
https://en.wikipedia.org/wiki/Combined_cycle; say 51% average), sends the
electricity to homeowners, who then run heat pumps (COP=2.5?). Crude math
says N BTU delivered / 2.5 / 0.51 = 0.78N BTU at the power plant,
neglecting line losses. Burning the gas at home would be N BTU @ 93%
efficiency = 1.07N BTU input, neglecting delivery costs. So using the heat
pump is a more efficient use of gas? Perhaps a district-scale,
combined-cycle NG co-generator that energized a central heat pump and fed a
district loop would be the best? Could one of these be built at each
existing powerplant, using the existing cooling water for a water-source
heat pump? The powerplants are not in-town, where the heat is needed. :-)
Dan J

Dan Johnson
510-325-5672 cell

On Thu, Nov 26, 2015 at 7:33 AM, John Daglish <johndaglish at gmail.com> wrote:

> No seems OK efficiency also varies with temperature, though it seems
> odd the sun is shinning no where else http://en.sat24.com/en
>
> see page 2 a standard flat plate collector  ... collected heat 45%
> http://www.lth.se/fileadmin/ht/Kurser/MVK160/Project_08/Fabio.pdf
>
> The Sunmark collector includes anti-reflective glass and some models a
> transparent anti-convection current screen between the glass and
> absorber reducing heat loss through the glazing.
>
> There is a 4000m3 of hot water storage at Sønderborg
>
> http://www.sonderborg-fjernvarme.dk/wp-content/uploads/2013/06/Solparken_folder_gb.pdf
>
> Expected share of solar heat in total annual plant production is 20%
>
> John Daglish
> Paris, France
>
>
> 2015-11-26 14:43 GMT+01:00 Don Lush <donlush at uniserve.com>:
> > Thanks John (Daglish)- Could you help me on the interpretation of this
> interpret this data.
> >
> > For example when I look at the current data (8:30 EST) from Sondorborg
> it shows current insolation at 939 W/m2 (which I am assuming is the
> incident solar radiation energy currently hitting the earth's surface at
> this location??)
> > It then shows current solar production at 442 W/m2 (which I assume is
> supposed to be how much energy is being generated by the solar array per
> m2.)
> > This implies a conversion efficiency of (442/939) 47% which is
> incredibly high!
> > Other sites have zero insolation and negative production numbers
> implying that they are consuming power.
> > How am I misreading this?
> >  Don Lush
> > Bolton Ontario
> >
> > -----Original Message-----
> > From: Greenbuilding [mailto:
> greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of John Daglish
> > Sent: November 26, 2015 6:58 AM
> > To: Green Building <greenbuilding at lists.bioenergylists.org>
> > Subject: Re: [Greenbuilding] Swedish solar-heated village
> >
> > Our Dannish friends are way ahead...
> >
> > Smart Energy Systems: 100% Renewable Energy at a National Level (Short
> Version) https://www.youtube.com/watch?v=S1P31EC0YsE
> >
> > Smart Energy Systems: 100% Renewable Energy at a National Level (Full
> Version) https://www.youtube.com/watch?v=eiBiB4DaYOM
> >
> > Solar heat fields for district heating   - real time production
> > statistics, not much today its cloudy
> > http://www.solvarmedata.dk/
> >
> > regards
> >
> > John Daglish
> > Paris, France
> >
> >
> >
> >
> > John Daglish
> > Paris, France
> >
> >
> > 2015-11-25 21:11 GMT+01:00 Dan Johnson <danjoh99 at gmail.com>:
> >> 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-45125D6EF8
> >> 95/0/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.c
> >>> fm/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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