Great Oak has finally, after years of trying to make the financing work, installed 19.44kw of Photovoltaic solar panels on our common garage roofs to feed our Common House electric meter (our local utility, DTE, requires the inverters to be tied to the single largest consuming meter for net metering). As of today, after various permitting and logistical hurdles, not to speak of the cloudy weather, we finally have some impressive generation!

GO South facing Garage Bank solar panels

The bright sunshine and low humidity today means that even though the sun is low in the sky, the panels, while producing about 12kw, or only about 50% of their rated capacity, are still producing more than the Common House is consuming currently, around 3kw:

GO CH current usage of electricity around noon on 12/24/2013

which means that since the panels are producing more than the instantaneous production, and that we do not have batteries to store the excess, they are feeding that back to the electric grid and GO is being credited for that — so the electric meter is running “backwards” (or would if we had the old analog style meter, but instead it shows a negative consumption instead on the digital meter!)

GO CH electric meter negative consumption on 12/24/2013

and for those interested in some details, we have 4 Renovo 5kw inverters tied together, installed by Srienergy, and financed out of our electrical operating budget for the Common House with the capital coming from our Great Oak Cohousing Association reserve fund.

Here is some detail from one of the inverters:
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It has been 5 years since the Great Oak common house was built and we have 5 years of heating bills. Unlike the factory built buildings with our individual units, the Common House is the sole, heated, stick-built building on campus and is comparatively very leaky. As a more affordable alternative to a full blown energy audit, we had an Infrared-only audit performed in November 2008. The auditors recommended we add insulation to our Common House attic as the quickest and least expensive step to reduce our energy bills. Unfortunately, they did not do a followup Infrared audit to see if that solved the most egregious problems. So, this year, Great Oak rented an Infrared camera (a Flir b50 from at $425+shipping  per week) to take pictures and compare. Here is a comparative set of pictures, with 2008 on the left and the 2010 on the right with a visible spectrum image in the middle of our sitting room fireplace mantle and above:

the before and after pictures look about the same, unfortunately, but the comparison is not entirely fair as different cameras were used and the auto-scaling of the colors to match temperature range might not be the same — the original 2008 audit pictures don’t have the temperature range shown so we can only guess that it is about the same as before or slightly better with the attic insulation. Which is disappointing.

A full table of comparisons may be found here.

Taking advantage of the camera, we also took picutres of the outside of all the buildings and various folks took pictures of the insides of their units.

Notable pictures taken in the Common House are shown below (all were taken after dark, after 9pm on a night when it was around 22 degrees Farenheit outside and the Common House is pretty much heated to 65 degrees inside). This first picture shows the residual heat in an uninsulated section of pipe coming from the solar hot water heater tank that feeds into the main hot water heater (natural gas powered).

IR 0145 SDHW machinery

Almost without exception, outside corners were several degrees colder than adjoining walls or ceilings, suggesting that insulation was not “wrapped” around, this was true of the factory built units as well – this is the NW corner of the CH sitting room:

IR 0150 sitting room NW corner

The North side of the dining room ceiling, with peaked roof shows a bright stripe across it where the hot water pipe runs to the East side of the Common House from the hot water heater, so although the ceiling is around 65 degrees, there is a 9 degree or so heat loss out of that water pipe and at least half of it radiates skyward no doubt pushing up our hot water bill — perhaps we should consider having a separate hot water heater on the East side?

IR 0153 dining room N ceiling

IR 0158 dining room N side with water pipe?

The next pictures are the water pipe coming down to the hallway
sink on the East side with one showing the heavily insulated attic
access panel (so heavily insulated now that I couldn’t push it up and
get in there to take “after” pictures).
IR 0169 W outside sink corner

IR 0168 E attic accesss

The 52 windows in the Common House are the major source of heat loss, though the blinds help to reduce the heat loss by almost half (just looking at surface temp) so we need to make sure we pull the blinds at night (or during the day in the summer) as it does really help. This is a North-facing window with a blind pulled half way down.
 IR 0184 dining room N windows showing effect of blinds

The pictures on the left are some dining room windows and the one on the right shows the play room windows — the middle one is clearly leakier than the other two:

IR 0155 dining room south windows

IR 0156 dining room south windows with peak

IR 0162 playroom window, contrast

The skylight in the game room is just a bit leakier than most windows, so likely a major source of heat in the hot summer:

IR 0166 game room skylight

and even though the LCD projector is in “standby” it is always warm, consuming a trickle of energy:

IR 0165 game room ceiling

the outside doors are particularly leaky, especially as they age fast and warp in the corners given the heavy use — this one is the NE door and the South main door (which is new but doesn’t seem to be terribly better than the original doors we had in 2008 other than it latches more firmly):
 IR 0167 NE door corner

IR 0129 south main door

A running laundry machine is a good source of radiant heat so we should keep the laundry door closed in summer, to the right is the aquarium, with around the same surface temperature:
IR 0170 laundry room (note extra cold window)

IR 1458 aquarium

Outside, the laundy vents aren’t particularly notable compared with the heat loss from the rest of the building, though having the sky in the picture does throw off the automatic ranging:

IR 0186 laundry dryer vents not leaking as much as joints 

the solar hot water panels don’t hold much heat at night:

IR 0181 Solar hot water
 panels not leaking heat 

and doors from the outside are somewhat leaky (notice my “heat” reflection in the glass):

IR 0176 N side main 
door from outside (notice my reflection)
a major source of heat loss seems to be the uncovered parts of the cement slab foundation, otherwise it is as expected, windows and doors are the major sources of heat loss and blinds do help. Some additional pictures of the North side:

IR 0182 east wing, notice slab leakage as bad as window

IR 0828 NW main doors

IR 0829 N side door

IR 0830 N side door and media room

and some of the South side:

IR 0172 general view, windows leak most

IR 0173 W wing, windows and doors leak most

In summary, adding the insulation to the ceiling made some difference but it is hard to be more specific. Given the structure that was probably the simplest change to make. The next best steps would be to see if can cover the exposed slab with insulation or at least some dirt (a building expert friend suggested that the best course of actoin would be to dig around 8-12 inches below the slab and then horizontally up to two feet underneat the slab and place foam insulation, but given the massive amount of labor and cost that would incur, it probably would not be cost-effective) and to try to cover as many of the windows as possible to minimize daily heat loss or gain as appropriate for the season.

energy , life in community , news

The Great Oak Common House has a Solar Hot water system installed to augment our natural gas burning hot water heater. The system produces “clean” energy using the sun and reduces our dependence on our natural gas supplier DTE. Details about the installation are available on our CH Solar Hot Water webpage. The system has been operational for over a year now. Our original estimates showed that we should expect on average to produce the equivalent of about 144 ccF of natural gas and if the price of natural gas remained constant, that should be about a $144 that isn’t paid to DTE. At that rate, it would take about 26 years to pay off the initial investment.

From September 1, 2005 through September 30, 2006, the system has produced in excess of 200 ccF and reduced our DTE bill by over $280! so we’re doing about twice as well as anticipated in terms of payback time, and that doesn’t even highlight the pollution we’re reducing.

According to’s calculator burning 200 ccF of natural gas will spew approximately 1.18 tons of carbon into the atmosphere, and offsetting that in a carbon market will yield anywhere from $6 to $16 at current rates.

CH SDHW collectors

Our solar hot water system produces clean energy, even in sunshine-poor Michigan, and even saves the community money by being independent of ever-rising natural gas prices.