Clean Energy Intro: What is an Inverter?
When we think about “clean” energy, we envision big, dark solar panels out in a field or on a roof. Or maybe wind turbines with those big whooshing propellers. What we don’t often think about are the other components that make solar panels and other technologies possible and practical for everyday use.
One very important component of these systems is the inverter. Inverters make it possible to hook your solar panels (or other energy dynamo) into batteries, your electrical system, and/or feed electricity back into the grid. An inverter’s most important task is to convert D.C. (direct current) electricity into A.C. (alternating current). In case you’ve forgotten your high school chemistry, A.C. is all the rage with the power company. Depending on the type of inverter you buy, they can pump all the excess electricity you produce into batteries or back into the power grid. And yes, the power company will pay you for the energy you send them.
So is there a catch? Well, all good things cast a shadow. You may be aware of solar panel efficiency, meaning how much power a panel can produce from sunlight. Inverters have efficiency ratings too. An inverter with 50% efficiency will successfully switch half of the D.C. current into A.C. current. That also means that half of that energy is wasted, but fear not! Most inverters have efficiency ratings in the lower-90% range. New breakthroughs in inverter technology could reduce the cost and boost the efficiency above 98% Speaking of cost, unfortunately inverters will cost you a pretty penny. They start in the $2,000 range. Inverters are rated (and priced) by their capacity, meaning how much power you can pump through them, so keep that in mind if you decide to buy one. The last issue is interference: inverters might interfere with your AM radio, walkie-talkies or even cell phones. Clever placement and some fancy wire work will reduce this.
Because of cost and efficiency concerns, one solar company decided to bypass inverters all together. Enphase Energy is trying to build solar panels with built-in micro-inverters that will cost less and offer more. On top of providing A.C. power, the micro-inverters will also include a communication feature that will alert the company if your panel needs maintenance. One less thing to worry about is OK with me!
Inverters are not just used for solar panels. Any device that produces or uses D.C. electricity needs an inverter to work with the power grid. That includes wind turbines and fuel cells. Some people with off-grid cabins in the wilderness forgo A.C. power all together and buy light bulbs, appliances, etc. that run on D.C. power. While this does remove a major step in their energy-producing process, it’s not particularly popular. D.C. power is low-voltage, so powering larger appliances becomes tricky. If you have more than a mile of wiring in your wilderness “cabin”, D.C. is a poor choice. It loses power as it travels over long distances.
Inverters bridge the gap between basic electrical production and practical energy use. They’re always getting smaller, less expensive, and more efficient as innovations and discoveries improve the technology. Now you know about inverters. Congratulations! I’ve included a few useful links below in case you’re curious about the details.
What’s the difference between AC and DC current?
Solar Expert.com: Inverter Basics
Solar Panel Info.com: Inverter Details
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February 11th, 2008 at 5:52 pm
I have a solar system in my home and my Sunny Boy inverter has a display on it showing how much energy is being generated. This is fascinating to watch because we can learn more about how the system performs.
Solar panels perform better in cooler temperatures because the panel efficiency is greater. Our system was generating the most energy I have ever seen yesterday, when it was sunny in Chicago and about 0 degrees F.
I’ve also seen the performance of the system drop considerably as a shadow comes across one of the eight panels. Watching the display on an inverter is a great way to learn these things.
February 11th, 2008 at 10:22 pm
I’m involved in community-based disaster preparedness – which, of course, benefits greatly from solar power availability. One of the puzzles we’ve been trying to solve is whether or not we can avoid using inverters altogether – since emergency equipment (radios, rechargeable lighting equipment) generally runs on DC. Why – we ask this question with no engineering background – convert from DC to AC and then back again to DC? Can we avoid this loop, save some energy and expenditure?
- thanks for your helpful article.
February 11th, 2008 at 10:52 pm
Yes, inverters are not necessary when all the appliances and equipment can run off of DC electricity. Without an inverter however, the solar system cannot be connected to the electric grid because the electric grid runs off of AC electricity. Special appliances and equipment are needed that can run off of DC power.
If you want to be able to run the DC equipment 24/7, batteries are necessary. The voltage of the batteries would have the match the voltage of the equipment being operated. 48 volt batteries are compatible with a 48 volt radio for example. Batteries do increase the cost and maintenance of the system, while lowering the efficiency. For disaster preparedness however that can be a small price to pay for having equipment when you need it.
February 12th, 2008 at 2:27 am
Ahh, the Edison v. Tesla battle emerges once again. Obviously, Tesla’s AC ended up winning, but AC has become so entrenched in our electrical infrastructure, it is creating some obstacles for the large-scale development of distributed generation. It strikes me that villages and small towns in the ‘developing world’ would best benefit from the the distributed generation model (not to say that US/Europe wouldn’t).
With that said, inverters are cool. I want to add one to my small RV’s ‘green overhaul’, so I can power more AC gadgets. I’ve already got deep-cycle batteries that recharge via the engine alternator to power lights, water pump, stereo, fridge, and other DC components. I plan on adding a little PV for the roof to charge those same batteries when I’m boondocked for a period.
It all sounds so great, but I also know it won’t be super cheap
February 12th, 2008 at 2:37 pm
I’ve been using a Trace for 15 years; some of my neighbors have used their Trace for 25 years. I am always tempted to buy a back up, as we would be screwed without it, but it is so sad Trace isn’t around anymore.
If you run DC, you need bigger, more expensive cables and need to house your system closer or in your home. By using an inverter, you can use “normal” wire and keep your batteries and other equipment further from your home. AC power also suffers from line loss, but it is less since the voltage is higher.
February 12th, 2008 at 7:14 pm
Jennifer:
Thanks for that info! I didn’t know about the heavier wires on DC power. I’m generally under the impression that if you decide to run your house on DC you’ll probably spend just as much money for the special hardware (appliances, wire!, lightbulbs, etc.) as you would to just buy an Inverter.
Can anyone confirm that?
February 12th, 2008 at 8:15 pm
The price varies widely on application. DC appliances can be very pricey because they are not common and it might be hard to find certain appliances. Wire costs vary depending on the distance needed. If a solar system is not connected to the power grid, one can typically use a cheaper inverter so that AC appliances can be used. The energy wave is a square shape instead of a round one, so some motors may have difficulty running off of it.
February 13th, 2008 at 4:57 am
Sarah, not all inverters use modified sine waves. Our old one did, and true, we had trouble with some appliances humming or their motors burning up. We have a true sine wave inverter now, but as I mentioned in my comment, it is not new (15 years old, at least). I don’t know anyone who uses straight DC anymore, it is very limiting. We had only a car stereo and lights when we ran straight DC.
Michelle, when electricity first was developed in this country, the great debate was DC or AC. AC was chosen because of the size of the wires and the line loss from the DC power.
February 13th, 2008 at 12:23 pm
Jennifer – oh yeah, Edison vs. Tesla as Tim Hurst mentioned.
There was an article about a new inverter breakthrough that also had a little inverter history, but I couldn’t find the page. My link and the corresponding link from Ecogeek didn’t meet the proper story. If I remember correctly (big if), there hasn’t been a major inverter breakthrough – until recently – in something like 30 years. They get smaller and slightly more efficient, but these new developments are very promising for the industry.
(http://www.ecogeek.org/content/view/1316/)
February 14th, 2008 at 1:44 am
Yes, I recently read about inverters being more efficient.
September 16th, 2008 at 5:04 pm
I got involve with the marketing of inverters about 3 years now and I have come to appreciate how wonderful the device is. In Africa where electricity fron the grid is in short supply and so a lot of supply outages, the inverter comes handy. The few hours of supply from the grid will be sufficient to store enough of converted AC in the batteries (as DC) which is reconverted by inverters whenever there is outage from the grid. The efficiency of inverter continues to improve. This is cheering. I beleive too that the cost will soon start to come down with improved production method and efficiency
December 11th, 2008 at 5:42 pm
Hi, and thanks for the info on inverters. I’m coming into this as a complete novice. I bought a 200 year old ex-watermill in France 4 years ago…. and for four years have been watching the streams which run thru my property pass away into the valley below. I’m determined to try to harness this wasted energy. I’ve a lot to learn, but I’m getting there.