The second lecture of Ene-59-4210 Special Course in Energy Economics was held on 21th January 2011. The topic of lecture was rural energy systems.
In rural areas in developing countries the main sources of power have been human and animal power. Biomass and charcoal are also burned for example for cooking and heating. Things have however started to change because electricity has been utilized more and more. In many cases there is no access to the electricity grid or the grid is not reliable enough so electricity has to be produced locally. These kinds of electricity systems are called Remote Area Power Supply Systems (RAPS). Because of electricity, many new appliances can now be used in rural areas in the developing countries. These include lights, TV, radio and water pumps, which do not require human power.
A RAPS can be powered for example with photovoltaic (PV) or small scale wind turbines. Both of these generation forms are intermittent and do not correlate with load so some kind of storage equipment is needed in the system. Lack of correlation comes from the fact that peak load occurs in the evening due to lightning but peak generation does not necessarily occur at the same time: peak generation for PV occurs in the middle of the day and peak generation for wind power is not dependent on time of the day. During the nights it is possible that there is no load or the load is very low.
Most widely used electricity storage equipments in the developing countries are batteries. There are few different types of batteries available. The most common type of battery used in the developed countries is lead acid battery. The reasons for that are it’s cheap price and reliability.
New knowledge for me on the lecture was some topics related to batteries as a part of small energy system and sizing of these batteries. I think that this knowledge can be applied also to Finland, for example for a group of summer cottages without access to the electricity grid. Aggregate load profile from summer cottages and generation of PV system and small scale wind turbine in local conditions can be examined and then the need for batteries calculated.
An interesting detail on the lecture was comparing of developing country of today to Finland some 50 years ago and what kind of similarities there is from energy use point of view. Another interesting detail was human power measured in watts. Human can work at continuous power of 75 W. Peak power can be ten times higher.