Solar Industries Solar Panel Arrived

I'm pretty impressed by the welded joint We can put some polycarbonate over it and try it out..

Solar Industries Solar Pool Heating Panel

Solar Industries makes an unglazed polypropylene solar panel with welded manifolds that basically looks like the absorber plate we have been contemplating and prototyping.

They sell through distributors, and Solar Services (757) 427-6300 is the one that will drop ship and sell at dealer prices for self-installs.

A 4'x12' panel usually sells for around $350. Dealer pricing is $172. That's $3.58/sqft.

Other costs include $10.28 for a "collector kit" (bracket, straps, connectors, hoses, clamps) and a $7.20 "resin surcharge." So that's $189/4x12 panel, or $3.94/sqft. Obviously, we would expect a significant price break over a DIY consumer cost if we used these in a product we marketed.

Also, it's $56.60 for a system kit with a vacuum breaker and coupling. One needed per system in their configuration.

The largest size by special order is 4'x18'

If we wanted to test one out, shipping is $50 for a box which holds up to two collectors.

Jason happens to have two of them with pinhole leaks up in Bimidgi. It looks like we will be able to get one down here later this week.

Which Windows will win?

Windows for the green house
Windows for the ARC
Windows for Dug's place
The choices aren't stark!

Introduction
Windows are an key part of any building. Especially so if you want to heat your building with the help of the sun. I have been trying to understand the basic performance issues involving glass, u value, local climate and solar gain.

Insolation
We began by looking at the amount of heat a window can gain. We looked up the solar incidence (insolation) for our location. NASA has big tables full of information for all over the country. So we got a table of information listing the number of btus/ft^2 per day on a south facing vertical surface for each month of the year here in Pine River.

Insolation for south facing, vertical surface

Month	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Solar btus/Ft^2/day	922	1123	1056	995	912	871	931	960	922	954	858	807

The heat gained from a window is the Solar Heat Gain Coefficient (SHGC) times the insolation. The SHGC is a function of the glass and every window manufacturer publishes it.

Heat Gained (btus/month) = Insolation (per day) X 30(Days/month) X SHGC

Heat Loss
Then we got information on our average temperatures to determine how many btus a window will lose. This document from Noaa has MN climatic data. http://cdo.ncdc.noaa.gov/climatenormals/clim81/MNnorm.pdf
So we got the degree days for Pine River. The degree days in this document are based on 65F, but in a super insulated house it is generally more useful to go with degree days based on 50F.

Heating Degree Days (HDD) for Pine River, MN

Month	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
HDD (50F)	1489	1112	785	275	43	1.8	0	0	45	319	918	1516

We multiply the degree hours per month by the windows U value to come to the btu's lost. The U value for a window is also published. Many web sites list the center of glass U value, but the frame around the glass makes a big difference, so you need to get the total unit U value for that window.

Heat Loss (btus/month) = HDD(per month) X (24 hours/day) X U value

Putting it Together

So the overall rating we are looking for is the ratio of heat gain to heat loss. Ideally we are looking for a window that gains more heat than it loses, on average for every month of the year. If we represent that as a ratio we get:

Heat Gained (btus/month) = Insolation (per day) X 30(Days/month) X SHGC

Heat Loss (btus/month) = HDD(per month) X (24 hours/day) X U value

The ratio on the left is the relative performance. The middle term is the location specific numbers that will change from place to place and with different solar panel orientation. And the third term is the window performance numbers.

In a break even, the Heat Gained over Heat Loss must be 1.

If we divide both sides by the location term, we get:

So, to get break even performance our window specs must be proportionate to the location specific term. If we revisit our tables from up above and format them to be per month, we get the following.

Lat 46.5	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Lon -94.5
HDH (50F)	35,726	26,698	18,835	6,610	1,037	43	0	0	1,080	7,646	22,032	36,374
Insolation (btus/month/ft^2)	27,649	33,676	31,667	29,849	27,362	26,118	27,936	28,797	27,649	28,605	25,735	24,205
Degree Hours / Insolation	1.29	0.79	0.59	0.22	0.04	0	0	0	0.04	0.27	0.86	1.5

The most important thing to note is that in our location, December is the worst month. To break even in December, we need a window with SHGC or 1.5 that of the U Value.

More later on which windows we find that meets these.

Plasma Table Fume Extraction

We were given the rough figure of 30 CFM/ft^2 for downdraft fume extraction. So that's 1500 CFM required for our 4x10 table. It seems to me that number could be off by 50%. The blower we have seems to output less than 1500, maybe 1000. Still, I don't think 1500 will be enough. We have a much bigger blower we can try out when we get a chance. It will have to be figured out before winter, when opening the doors isn't an option.

Corrugated Plastic Price

I got this quote on corrugated plastic from Daniel Damas-Manager
Laird Plastics:

"The material is priced out at .69/per square foot. There are not price breaks because it is a custom run material. The minimum is about 4 skids (approximately between 800 to 1000 sheets of material)."

I asked, "What product is this price for? We had samples for 5mm 1500 and 2000 gram. I'd also like a price for a non-custom but similar product in the same sort of quantity. "

A really interesting addition - they mentioned that someone did something like what we are talking about. I didn't think they would ever give us more information, bu they did:

"The most active company using this in an application similar to what you are thinking about is Calypso Water Jet out of Dallas, TX. (Website is http://www.calypsowaterjet.com/). Apparently they make parts for some one who uses it in a solar panel application. Hopefully this helps you out. "

I think we should tell the waterjet company we may want to buy their customer's product rather then make it. With all the idea stealing, they may still be cagey...

update: 7 May 08

Per Dan at Laird:
"The price is the same for either one of the 5mm black product, they do not run any faster than the other. Standard off the shelf 4mm fluted sells for about .30/square foot. As we discussed the everyday stuff is a much lighter weight product. There is nothing close to this that is a standard product."

update: 8 May 08
The waterjet company was a bum steer. They use the Coroplast as a consumable backstop for their waterjet cutting. Well - I have to give them credit , water is involved .

Build Smart Summit

The Build Smart Summit was put on by Region Five Development Commission, and they plan to keep related green building developments updated on their website.

Randall Arendt presented. His website had several links to case studies of conservation subdivisions as well as other helpful information.

We learned about a group called 1000 Friends of Minnesota doing sustainable development study and promotion. They were part of (perhaps leading) the formation of the Brainerd Lakes Area Conservation Collaborative (BLACC).

update 5 May 08:
I found my second page of notes (I knew there was more than that).
More links:
Community Associations Institute - Resources for setting up community associations.
Minnesota Green Communities - For creation of affordable, healthier, and more energy-efficient housing.
Green Institute - Reuse, green building, community based energy, gardening.
Central Minnesota Build Smart - Local website under construction, for promoting green building.
Smartwall Company - They factory make sprayed studwalls with windows pre-installed.

Building Energy Auditing:
Home Energy Saver - Government DIY home energy audit
Energy Star - Another DIY Audit
US DOE - Consumer's Guide to Energy Efficiency and Renewable Energy

Software:
EnergyGauge - Code Compliance and Home Energy Rating Software
Architectural Energy Corporation - REM/Rate and other similar software

Glass

Gull lake Glass checked with their supplier and they claim tempered glass is required.

For 5,000 ft^2 of 1/8" tempered glass, our cost would be $2.90/ft^2

Rubber Absorber

We got a quote from Delford Industries company for a rubber formula for the extruded absorber material.


For a 10,000 ft production run, our cost would be $1.95/ft^2

The tooling cost is only $350. The product cost is basically for material plus time, they couldn't suggest a refinement that would save money.

Corrugated Polypropolene Absorber Test

At 42 degrees at noon facing the sun on a somewhat hazy day, maximum temperature is around 260F stagnated in an insulated airtight enclosure, with 6mm twinwall polycarbonate spaced about 5/8" from the absorber face.

Coroplast

http://www.coroplast.com/product.htm

We got samples of the 5mm 1500 and 2000 gram/m^2. Typical weight is 1000 gram/m^2.

They are one of the leading manufacturers of corrugated plastic sheet. Maybe that's why getting their attention is so challenging. Here is the best contact I have found: Peter Maurer 606-796-0334 x 3422