Roll-your-own piecemeal solar: silly idea?
I'll be going camping soon in a sunny place, and was thinking of using this trip as an excuse to start on a long-term project of building my own grid-tie PV (photovoltaic) solar system at home. I'm asking you, person who probably arrived here via a search engine, whether this is a workable idea.
Allow me to play the part of Basil Exposition for a moment: "As you may know, gentle reader, grid-tie systems are connected to the electricity grid, which generally means that they supplement a home's electricity, rather than being the sole source of it. A typical system consists of some PV panels that convert solar energy to DC electricity, an inverter that both converts the solar DC power to AC and connects the system to the power grid, and optionally a charge controller that delivers power to deep-cycle batteries, which store excess power for use at night time."
For the camping trip, the basic strategy is to buy one of each part of the system that can be bought piecemeal, and then buy inexpensive, relatively throwaway versions of parts that are expensive in a full-blown system. I'd buy one 120-watt panel (about $600) and a cheap charge controller (about $50). I'd then use a couple deep-cycle batteries and a little inverter that I already own. On the trip I'd use this power to charge various battery-powered devices, such as a laptop computer. (We'll ignore the annoyance that I feel knowing that 12-volt DC gets converted to 120-volt AC and then back down again to around 12 volts to charge batteries, no doubt losing at least 40% power in the process.)
On my return, I'd put the panel on the roof of my house and try connecting my desktop computer to it (via a UPS so I get a warning if power's low). I use that computer for perhaps a few hours a day so it should work.
Eventually, after research, and hopefully your feedback, I'd shell out money for a real grid-tie inverter (at least a couple thousand dollars) and charge controller (also thousands of dollars), and then add a few more panels and batteries. If the efficiency worked out, then I'd scale up the system -- having already bought inverter and charge controller capacity to handle the extra power.
The alternative is just coughing up $40,000 and having someone come in and install a complete system this weekend on my roof.
Advantages of the roll-your-own approach? It's an interesting hobby project; it commits less capital up front. To the extent that PV panels come down in price as technological advances occur, I get the benefit of lower prices in the future.
Disadvantages? It might fail because I don't know what I'm doing; I get the worst possible return on the large components until I fully utilize their capacity.
What do you think? Silly idea?
I love this idea! I wish I understood this a little better, but the idea of starting small and scaling up gradually makes a lot of sense to me. The part I'm having the trouble understanding is the point where you connect to your home's system. I don't know much about electricity, but I do know there's one set place where the power from the street enters the breaker box. It seems you'd have to connect to the grid upstream from your breaker box, but how? Is there some sort of device for that or does this take an electrician?
Nicholas, the inverter is what you're thinking of, though it takes a special kind of one to do the grid connection. It takes DC input from the PV array and/or batteries as well as AC input from the grid, and supplies AC out using whichever power source is appropriate. You'd definitely want an electrician to install it for you -- excellent opportunity to kill yourself otherwise.
I believe this is called a grid-tie inverter, and it has the additional feature of letting you sell your solar power back to the power company -- though at wholesale cost, which is pretty cheap.
The most important thing to remember is that the panel is always ON, and can produce dangerous currents. Use DC disconnects, the ones that will overcome arcing across the contacts. Do Not use common AC rated equipment. Go to www.nmsu.edu/~tdi/roswell-8opt.pdf for the bible of photovoltaic info. John Wiles is the guru who has pioneered safe use of PV. The system is obviously uneconomical, but if you want it, go for it. Another site is www.nmsu.edu/~tdi/photovoltaics/codes-stds/codes-stds.html for a checklist. Home Power Magazine also has 10 years of stuff for review.
John and Mike -- good info, especially the links. Looks like the URLs were outdated, though. The PDF redirects to: http://www.nmsu.edu/~tdi/Photovoltaics/Codes-Stds/PVnecSugPract.html
I did a little googling around based on the info in your posts and am realizing all over again how much I have to learn about this stuff. (I'm blogging occasionally about these issues as I try to educate myself about renewable energy solutions, but it's an incredible amount to learn.)
There are two main questions I'm pondering right now, based on your thoughts:
- The inverter seems to be the key to attempting any sort of off-the-grid or self-subsidized solution. Yet, when I searched around briefly, I'm not finding any clear guidelines on what one needs to get started let alone anyone selling such a component. Could this be part of the reason self-installed (realizing a licensed electrician is probably mandatory) solar hasn't taken off?
- The note about these solutions being uneconomical definitely hits home. In order for sustainable energy solutions to take off in the U.S., they need to pay back quickly so I'm only considering affordable solutions right now. I know the panels themselves have dropped substantially since the early days, but are other components keeping the total cost of ownership too high to be a worthwhile investment?
(this may sound like an ad/spam, but it's not!)
I saw this in the USAToday at the hotel the other day, and seems it might be of interest?
http://www.uncommongoods.com/item/item.jsp?itemId=14526
"This remarkable bag not only stores your stuff, it also recharges your electronic devices - using solar power! Great as a small daypack and laptop bag, this creation harnesses the energy of the sun to power your iPod, cell phone, PDA, digital camera and more. Including a 2,200mAh Li-Ion battery to store power, the bag can also hook up to an included travel charger and car charger when you're out of the sun. When you are in the sun, the solar panels are tough, lightweight and waterproof and they generate up to four watts of power. The bag can be worn as a backpack or sling bag and features an intricate design that features a mesh backing for air flow and wire channels for headphones, hands-frees and more. Fully padded to protect a laptop, it fits up to a 15" screen and also has loops to attach to other backpacks and rucksacks. Picked by Shiny as the 2005 Green Gadget of the Year.
Hi Mike
Ik would like to elaborate even more on your idea ... I live in Suriname where we have al lot of sun but no technology available.
I'm building my own house and the utilities company just hooked me up for some temporary power (for the construction period).
Lucky me I got (from my dad's boat) about 1400Watts of solar panels but no inverter and no charge controller and these items are not readily available here.
I recently acquired an old Trip-Lite 2200VA ups with worn down batteries.
I'm thinking to myself .. a simple computer UPS does all you want to do ... it provides inversion, battery charging and even fall-back if AC power fails .. now we would like the opposite ofcourse ...
If only solar available (meaning grid AC is off) use that but protect our batteries from discharging to much .. no problem here as the UPS does this ... we only have to shut down the annoying beep comming from the UPS.
On the other hand we should protect our batteries from beeing overcharged .. that's a problem I need to solve because the solar panels keep charging and the UPS has charging option but only on AC .. best would be to modify the UPS design for this purpose... or else use a charge controller on the PV cells.
The other opposite if you're back at home ...
Use as much of the UPS (With the connected PV cells ofcourse) and if excessive power is required switch to Grid power ...and keep my batteries charged ofcourse... preferrably via PV and if battery power drops too far charge at any available source (PV and/or Grid).
This is the situation where you in fact overload (controlled) the UPS and it switches off .. but now it switches you to the grid directly... with thresholds and delays... e.g. start your laser printer ;)
You situation 1 should be simple .. look for an old PC UPS and hookup the PV charger directly to the battery .. connect all else to the UPS.. sell the inverter on eBAY.
Regards
Theo