If you had seen conventional power plants, you will know that they are large. Typical coal-based or natural gas based power plants are 100 MW or above in size – many of them over 500 MW. Nuclear power plants sometimes can be beyond 1000 MW even. The world’s largest coal power plant is a 5500 MW beast in Taiwan, and the largest operating nuclear power plant (2016) is an even bigger beast – 6300 MW in Canada.
Neither our grandmothers – and nor I suspect our grandchildren – will be pleased to see such large coal plants, but there they are.
Coal and other thermal power plants today mostly run on what is called as the Steam Rankine Cycle, in which superheated steam turns a turbine and generates power.
However, one drawback with this system is that these work at good efficiencies only for medium or large scales – the minimum such power plants can run are 5 MW and above. Which is fine for conventional power plants, as they run on fairly large scales, as mentioned above.
What if someone wants to use a 24×7 source of electricity generated on a small scale at rural and other remote locations? Neither solar nor wind power can help as both are intermittent. One can use biomass instead, as biomass is similar to coal in the context of its ability to supply 24×7 power.
But how can we run biomass power plants on a small scale if the Steam Rankine Cycle is not efficient too run a small power plant that is just a few 10s of kW?
This is where the concept of biomass gasification comes in. Through gasifying biomass into a synthetic mixture of gases, it is possible to run small scale biomass power plants.
The way it works is as follows: Using equipments called Biomass Gasifiers, biomass is converted into an organic mixture of gases called Producer Gas. This producer gas can then be used in a gas engine (not very different from a diesel generator) to generate electricity. As gas engines can operate on very small scales (even 10 kW or lower), we can this generate electricity from biomass on a small scale too.
For this reason, biomass gasification is quite popular for rural electrification schemes in many developing and underdeveloped countries.
In the past many years, I have had the opportunity to visit some of these small scale gasifiers installed in rural locations. Technically, they work fine, and I am convinced that these gasifiers constitute one of the feasible solutions in the overall renewable energy basket for rural electrification.
The only challenge I observed had to do with the gasifier maintenance. You see, while the gasifier itself might not require much of maintenance, the gas engine that uses the producer gas to generate power requires maintenance. In many rural areas, such maintenance was difficult owing to lack of trained personnel, and this had resulting in their mal-functioning or shut down.