Solar Guerrilla movement - Grid Tie Inverter to feed back to the grid

"Solar Guerrilla" is a term applied to a person who connects a small-scale solar generator to the public grid (and feeding electricity back) without permission or knowledge of the grid operator.

With the proliferation of affordable small-scale wind generation systems, the term Solar Guerilla also has been extended to include that type of usage. However in most urban areas, wind power is not viable so nearly most of the time the term is applied to solar PV systems.

Normally, in order to feed electricity back to the grid using a Grid Tie Inverter (or grid feed, inter-tie) and be paid for it, net metering is usually required. This means a professionally installed system, with safety sign-off, permits from the grid operator (distribution authority) and sometimes applicable insurances bought.

In the good old days with mechanical (rotary) meters, the meter could even spin backwards if the production of the small-scale generation system exceeded the power consumption in the home. Although, some countries or jurisdictions (such as the United Kingdon) mandated the use of ratcheted meters which are prevented from running backwards.

The same is true for the newer electronic (or smart) meters. By default, they are not set up for net metering. They won't count any electricity fed back to the grid, even if such a flow occurs. The electricity utility company must specifically configure the meter to allow net metering. And with the newest of smart meters, an alarm would alert the utility should an unexpected backwards flow be detected.

But feeding electricity back into the grid shouldn't be an issue if the system is only 100 or 200 watts (as such systems commonly are). In many cases, the daytime base load of a typical home would exceed 200 watts anyway, so all the grid tie inverter would do is to slow down the meter. At least there will be less consumption from the utility, thereby reducing the cost of the next electricity bill. A small 200 watt system would only generate around 1 kWh per day, which barely makes up for the typical 10 kWh daily usage by home appliances.

Although the concept may sound dangerous, in many cases, it is quite safe if done carefully by a knowledgeable person. Most Solar Guerillas use commercially manufactured Grid Tie Inverters, and it is as simple as connecting low-voltage solar panels (e.g. 12 - 24 volts) and plugging the GTI into a mains power point (outlet). No live mains wiring is exposed, and the GTIs have an 'anti-islanding' safety feature which will shut down the inverter's outout if it detects a grid blackout, such as when linesmen perform work on the power lines.

Having said that, non-approved GTIs are almost certainly illegal in most states of Australia (as well as most other countries). At the very least, you'll need to notify your electricity utility of your intention to run a small-scale alternative power generation system.

But for most hobbyists and backyard experimenters, it can be quite facinating (and even addictive) to dabble in green energy production. Still, be aware - a fire caused by an illegal GTI or grid-connected solar power installation may not be covered by your insurer.


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