Over the last year I have been part of an international team designing and implementing a solar mini-grid village electrification project in Myanmar. Last month we visited four of the villages and presented a training program for the villagers to begin the process of educating them about the community owned power system they will soon be enjoying.
The most important thing about off-grid solar power systems is that they need to be understood as whole systems, with limited inputs and outputs. The solar panels put energy into the battery, the ‘loads’ (lights and appliances) drain it out. If there is not enough flowing in to keep up with the draining out, the battery will be emptied and the system will fail.
We use water to explain electricity because it flows in similar ways. The water in the bottle represents the energy stored in the a battery. The cups are solar panels, each providing what they can when they get re-filled by the Sun. Wooden stoppers represent switches that open up a flow of energy out of the battery.
Lead-Acid batteries should be fully recharged EVERY DAY when the Sun is shining. It is important to keep the flow of power OFF when it is not necessary! Let the cups of solar power flow in!
These systems will use pre-paid energy meters at every house to control consumer access. The solar PV systems are sized to provide a small amount of energy to each household every day for efficient lighting, phone charging and small electronics. To help ensure that consumers do not use more energy than the system can provide there will be 50 Watt power limiters at each consumer connection. This will prevent the villagers from using rice cookers, tea kettles and other high power consuming devices not appropriate for use with off-grid solar power systems.
There is almost always a little leaking from the battery due to inefficiencies in the system. The worst culprit are inverters, devices that turn the direct current (DC) in the batteries into alternating current (AC) to distribute to the consumers.