Renewable Energy

We listened to a brief lecture today delivered by an MIT researcher working on renewable energy here in the Azores. One interesting point he brought up that had never even occurred to me was the fact that the implementation of renewable energy, particularly in isolated grids such as the islands of the Azores, is limited by factors that include both the amount of consumption and the variability of renewable power generation (e.g. wind energy requires the wind to be present, and the amount generated depends on the speed of the wind). This is the case because that any energy generated must either be consumed or "stored" by way of converting it to another form of energy or being contained and controlled so as to not overload the rest of the electric grid (which would include that shiny iMac or HDTV). As such, on an island such as Terceira, renewable energy, such as wind, make up only a portion of the total amount of electricity generated and consumed. The variability of wind generation is offset by the control possible over fuel-based power generation, which can be scaled up or down relatively easily according to consumption demand.

The researcher also described an interesting solution that another island has implemented with regards to buffering the energy generated from renewable sources. Essentially, a giant battery takes the form of two water reservoirs. One reservoir is at a higher elevation, and when water runs down from one reservoir to the other, electricity is generated via turbines. This energy can meet extra consumption demand when necessary. In the case where there is not enough demand and where there is excess electricity generated from renewable sources such as wind or geothermal activity, that electricity is used to pump water from the bottom reservoir to the upper reservoir, essentially converting electric energy to a different form, that of (potential) kinetic energy. Thus, this two-reservoir system acts like a giant battery! Someday, when the problem of buffering against the variability of power generation and consumption is more easily addressed, isolated grids, such as those of the islands of the Azores, will be able to move towards having 100% of their electricity generated from renewable sources.