Inverter

The inverter is probably best described as the nerve center of a house sized alternative energy installation. Most if not all of the wiring comes together wherever you decide you want to place the inverter. Also, because there are some really fat cables running between the inverter and the batteries you probably want to place the batteries as close to the inverter as you can.

So, what does an inverter do ?

An inverter converts the DC voltage that your batteries use (48 Volts in our system, but other voltages are being used, 12 and 24 volt most frequently) into an AC voltage that your house appliances expect. Technically speaking it is possible to have a number of your house loads powered directly from the battery, in practice however this is not very useful because the losses in the wires would be very large, and the cost of converting all these devices would quickly outpace the cost of the inverter. Any serious house sized system uses an inverter of sorts, and wiring up your house with car lights simply isn't an option.

Inverters come in many shape and sizes, $50 ones that you can use to power a radio or cell phone charger or small laptop from and $100,000 ones that you can run a whole hospital off. Clearly the first is too small and the latter is way too big. Midrange (so house sized) inverters are available in the 4,000...10,000 Watt range.

There are two main 'kinds' of inverters, those that make a 'pure sinewave' and those that do not. Now what is it that makes a pure sinewave inverter a desireable item ? Most of the equipment in your house was designed with 120 V AC (or 220 V AC if you live in europe) in mind. A pure sinewave inverter tries to come as close to 'grid power' as is possible by closely matching it's output to this desired wave shape. A 'modified square wave' inverter (the alternative) attempts to do the same thing, but goes about it in such a different fashion that the output is not even close to something that you can call a sinewave, even with a lot of imagination added. The result of this is that equipment that uses sensitive electronics (computers, faxes, photocopiers, scanners and so on) sometimes refuse to work on this kind of power. The advantage of a modified square wave inverter is that compared to the pure sine wave variety they are very cheap.

Inverters nowadays contain just about everything but the kitchen sink, the feature list of some of these includesL:

* inverter core (DC->AC at a certain power rating)
* charge controller
* battery charger
* grid-tie interconnect feature (allows you to sell excess energy back into the grid)
* pass-through switch to get excess power required by your appliances from the grid
* generator remote control (to switch on your generator when your batteries are low and there is not enough sun/wind in an off-grid situation to power your loads)

In our configuration we have decided to use a 4000 Watt Trace sinewave inverter, with the option to add a second one at a later stage (they can be 'stacked' for 240 volt operation (that's not the same as using them for 240 volt operation in Europe, this is 'North-American style single phase 240 V', Trace makes European models which probably have their own 'stacking' scheme).

A word about Trace, you have probably noticed that their name comes up quite a few times in this whole site. We are in no way affiliated with them, but I could not help but notice a few things about their company:

* They seem to have pretty much cornered the market in selling alternative energy equipment that is designed to work in house sized systems
* They are pretty expensive
* They are not too very friendly (from what I have heard this is since they have been taken over by Xantrex)
* They have recently shifted their production to the far east, and it remains to be seen if they can keep their quality levels up
* They always repair what they sell, but it will cost you

Now from all of the above you can see that I would gladly buy from some other manufacturer, but as it stands today nobody can hold a candle to Trace. I really hope that there will be some competition in this field because they sure could use some.