What do you mean? PV or DHW?

I have two arrays of photovoltaic solar panels that generate 11+KW peak. If anyone has any questions, I'd be happy to answer them.

Wow, that's a lot of PV. My parents have a 1.5kW array, and that cost a pretty bunch. I'm still intrigued what plant.babies wants to do with 'solar panels'. Plants generally don't use much electricity...

It's to provide electricity to the greenhouse heater.

I read that a solar panel array costs to much, and doesn't pay for itself for a long time (12 years for some)

:)

You seem to be asking a lot of questions about solar adaptations in GHs
I have a dome that does a lot of this stuff.
You might check out the website of the company where I bought my kit.
Or....I could share.
www.growingspaces.com
Kathy

Nathan -

Electricity from PV (or other source) is not required but desirable, depending on your goals. PV electricity offers many uses, if one can afford a system, or aquire used PV panels, or individual PV-powered appliances.

Need/benefit from Fans, heaters, grow lights will vary depending on the month, amount of shade, and level of weather conditions.

Bottom heat is great for success in propagating lots of types of plants from stem cuttings (roses & shrubs) and leaf or tip cuttings (lots of house plants).

Heaters use a lot of electricity however, so I may not attempt electric space heating for winter. Instead, I'll probably use passive and manual methods to improve my growing in Spring and Fall...and see what might winter-over from basic protection & passive solar storage. I'm familiar with creating cross-breezes from living in good old houses, so the first season I''l see If i can get by with that. My housemate will also let me try his inexpensive Solar Fan before I Buy my own.
After buying a nearly useless one years ago, I'm a bit skeptical about the brightness of Solar Lights. So electricity from the house, or PV, might probably make sense for lights. You can use a light bulb below flats as a cheap bottom heater for flats and cuttings; and use water filled jugs to absorb and store passive solar heat for a modest season-extender. A few degrees of comfort can make a difference for some plants.

Many plants won't germinate until the soil is 50 degrees, others need over 70 degrees. Bottom Heat alone can start some heat-loving seed varieties. Many seedlings stall out in the Spring until they get a couple days of hot weather -then they take off and really get productive. Affordably accelerating the next growth stage is a goal, even if just for some plants, for Spring--only Season-Extending Greenhouse gardeners. Extending the Harvest by keeping Tomatoes and peppers going in the fall is wanted by others. maintaining the day-length that makes ripening happen can be extended using Solar Electricity.

Most seeds can get going just fine outside using Winter-Sowing (see the WS Forum) But especially in cold climates, getting Heat-loving veggies like tomatoes, basil and peppers going months early is often the happiest reason to have a greenhouse. To start everything earlier, and prevent the usual spring-stall-out of growth, and increase odds of survival, using light bulbs or electric heaters can make a real difference. (I assume Fans are desired because air flow, light and & ventilation reduce fungus and mold from humidity...and wind makes stronger stems, and can quickly help cool an accidentally overheated greenhouse)

In some regions, seedlings started outside can get brutally pummeled and ruined by rain and hail. Then there are the critters and slugs, that go after many smaller seedlings. Calamities can affect success inside the GH too, but the goal of having micro-climate-control equipment is to selectively reduce the risk.

In areas where the Spring keeps you indoors feeling gloomy, working in the GreenHouse can lift your spirits. I plan to bring Springs of fragrant herbs in to add to that experience. In Winter/early Spring you need light both for heat/comfort and for plant growth. In fall, comfort and continued ripening. Indeterminate Tomatoes can keep on setting fruit too...so they'd be a better choice than determinate Toms.

Some Gardeners use their GreenHouses 12 months a year, for food, orchids, african violets and many other plants. In cool and cold climates, adding insulation, electric heat, and light sources makes this an option.

I'm a newbie to Greenhouse growing myself, but have been getting ready to get mine by reading about it for awhile. I have just enough experience with failed plant experiments, stalling after WinterSown sprout success, and Slugs during hardening-off to appreciate the possibility of greater success another way. So I might use a combination of Passive and Photo-voltaic Solar-options in my new GH.

I intend to use a cheap thermometer and manually adjust shade to keep seedlings from getting cooked. I really like the idea of allow Cukes to grow up a wire frame to provide some natural shade in season. PV-assisted light inside, on a day-length adjusted timer for optimum growth and ripening would be wonderful.
My personal challenge will be to keep (seed-drying refer to the thread: Seed-Saving Nutcase) and other non-growing stuff OUT of the GH. Remember: the new GH is NOT a Shed or granary!

Hope this summary helps someone think through their GH choices.

Jules

pdxjules,
I don't think PV for lighting is a very good idea. You'd be better off collecting that light with plants or thermal means. I gather you haven't done the maths (economics) on this idea to see it is not very practical yet. $20k will buy you somewhere around 2kW of peak output, but this is the output when the sun is shining bright in summer - just when you don't need additional light. When panels are comparable in price to other roofing materials, this will change.

I think a much better idea is to design the greenhouse to collect as much light as possible and store that as heat.

I agree that greenhouses should be a refuge from the weather - my second half greenhouse will have a reasonable area set aside purely for sitting in and drinking tea. However, greenhouses for tea drinking are not compatible with cuttings, and greenhouses for cuttings are not conducive to tea drinking, so I'm keeping them separated with an internal partition.

Jules, What solar fan does your friend have? I am looking for a solar fan for my greenhouse.
Oddly enough I found that home depot has two solar attic vent fans ! I may be able to adapt them to my greenhouse. i am still looking around however.

-renee

11KW is a lot of solar. NJ is offering $5/watt rebates on solar panel installation, and 10KW systems around here average $8/watt. The buyback is currently around 6-7 years, but with energy prices going up, that'll come down a bit.

The only reasonable use for solar panels (as opposed to solar devices, like ventilation fans) that makes sense is to hook them up to the grid (i.e., into your electric panels) so you can sell the electric back to the power company during the summer and buy it back in the winter. Otherwise, you'd be generating electric during the day, when you don't need heat and light, and using it at night, when you do.