And idea and a Harbor Freight kit... where to from here?

[doodaa]

 

  I'm a, let's say middle aged, guy who's worked with electronics about half my life. Unfortunately the theory was never my strong suit but I haven't run into many sysytems I couldn't fix that someone else designed. The latter part of my "career" has been computers, meaning parts swapping and not "real" elex work. In brief, I've heard of Ohm's Law but when it comes to using it, talk down to me.

 Well, the other day my lovely fiance asked me if I could build her a greenhouse. Told her sure I could... but on my 45 minute commute home from work I got to thinking about powering said greenhouse using PV panels, shouldn't be a big job (10'x12') and I may mess around and learn something. Hey, I live in the "Sunshine State" why not right? After casting about the Internet some I came across you good folks and after some reading I decided I'd go for the Harbor Freight kit and a different controller since those piezo buzzers really aggravate me. I'm guessing this will be plenty to power a ventilation fan and some lights so she can grow her tomatoes and flowers in the "winter" we have here. I've also tossed about the idea of powering my household well with solar which would be handy since I also live in the "Hurricane State" and am out at the end of the grid, at least the end when they're prioritzing repairs. This led me to thinking about adding enough capacity to power the whole place after a storm... a thought quickly discarded after reading the advice here. There's just not going to be enough $$$ to do that anytime in the future but I do see some possiblities for a larger system after my ignorance subsides a bit. I've also got a carpenter friend who has an off grid hunting "lodge" he'd like to use PV in so maybe there's an opportunity to spend someoe else's money and learn too.

I'd also like to thank those of you who share your knowledge here. You've already taught me much and saved me some money. I was thinking starting bigger, meaning more $$$, and you've convinced me that starting with training wheels is the better way. I'll be back once I have some specific questions... any advice, opinions, constructive criticisms you'd like to offer, I'd be glad to hear.

[Countryboy]

Solar tends to be costly, in terms of watt per dollar.  Hydro or wind is usually a cheaper source of energy, but requires more maintenance.

Decide how much money you want to spend.  You will probably be further ahead to spend X dollars on better insulating glass, than to spend X dollars on solar panels.

You need to figure out what fan you will be using.  How much electricity does it consume, and how many hours per day will it be running?  What lights do you intend to use, and how many hours per day will they be on?  How efficient is your battery bank?  Once you have determined your daily consumption requirements, then you will have a better understanding of how many watts worth of solar panels you need.

If financial cost is your primary concern, I'd probably recommend looking at building a wind turbine, unless you have a hydro source available.  

[DanG]

A HF 45 watt kit might net 200+ watts on a perfect day though after losses would give you 150 watts usable, any clouds during the solar noon '5-hour' window you will get considerably less, which is the main problem with solar in Florida, clouds building mid-day...

200 watts may give you some water pumping to refresh a gravity feed drip irrigation system and some 12V compact fluorescent area lighting for after-dark chores and perhaps a motorized vent damper for passive cooling - but not much else.

Tomatos are notoriously hard to cultivate in winters' short days without large lamps to extend the day length, I believe that 5 hours solar noon maximum would need to be extended 3-5 hours both AM and PM so that is 2.5 to 10 KW per day for about half of your greenhouse area in keeping tomatos fruiting, that is if you want to spend $$$ on horticultural lamps and pay the electric bills. If you do that connect the hot-house to your home to use their heat instead of venting it away.

Fluorescent lamps are not as efficient and would need to almost touch the plants and so would shade them from sunshine if not moved daily - and its almost impossible to find bulbs in a spectrum that tomatoes like, I've tried up here in Minnesota to jump start them w/o sunshine to get a ripe tomato earlier than 3rd week of July but only get weak plants that look more like crawling vines.

Hope someone w/ sucesses posts, interested to see where this goes!

[DanG]

To further complicate things : )

http://tinyurl.com/mk6s3 <--- great greenhouse material, good site and best prices I've seen...

[thefinis]

You don't need to try and keep the greenhouse warm in Florida you have to try and keep it vented when the sun is shining. Being able to seal it fairly tightly for the few times of freezing temps should get you by unless it is one of those rare times when the groves freeze and the orange crop is lost. Then for a small greenhouse try using one or two of those old kerosene wick lamps. All you have to do is keep it above 33f for most stuff to survive 40 for some of the tropical plants but anything lower than 55 and the tomatoes won't set fruit. You can extend the tomatoe season on both ends but in the middle of winter expect to only grow tomatoe plants not tomatoes. Sorry but you are big money ahead to just go to the store in the middle of winter for tomatoes rather than try and control climate and light to make fruit.

What ever skin you use make sure it is UV protected. It will last much longer if you can take down the skin and store it in the summer. Put a sunshade say 20% blockage for a roof in the summer when the winter skin is stored. Expect the greenhouse to be one of the first things to go when a big blow hits. For the winter time try and come up with a way to roll up the sides to vent. If you want to use forced air venting one way to is the solar attic fan which doesn't use batteries and only runs when the sun shines can come with a thermostat. They are a little pricey running 300 to 400 but that may be close to a HF setup with a similar fan but no batteries. 10 watt solar vent unit 850 cfm and the 20 watt unit 1200 cfm.

For a hunting cabin that only gets used for weekends solar panels and a battery bank will probably work as they get a chance to recharge between uses. You can also boost or back it up with the truck battery if things get desperate. For a house electric backup for well etc after a blow get a generator one that will run the well and/or the fridge and freezer. The solar panels you are counting on may not survive the storms.

just my 2 cents

Finis

[tecker]

Some 55 gal drums and an activated compost pile (As large as you can make for the winter) .I grow tomatoes in containers . I dig large holes and fill with compost and place the drums with water over the compost they don't get hot bu they don't frezze . Double glazing is important .

[Bruce S]

My favorite place for grow lights.

http://www.growwithleds.com/index.htm

Also, there are solar powered vent fans, these range from out-house sized to production greenhouse sizes.

Bruce S