Introduction to hydroelectricity in New Brunswick:
Water being pulled by gravity to points of lower elevation contains potential energy simply because it could fall from a higher to lower elevation (and perform work as it falls). The central concept of hydroelectric facilities is harnessing the stored energy of water at elevation. The higher the water, or the more of it that there is, there greater potential for energy generation. Both variables can be increased by the use of dams (of rivers or waterfalls) that greatly increase the amount of stored water or its height. Once behind a dam, water is allowed through a relatively small channel, called a penstock, where it comes in contact and spins a turbine. See Figure 1.
Figure 1. Schematic of a hydroelectric facility. http://www.nbpower.com/html/en/safety_learning/learning/electricity_generated/hydro/hydro.html
The spinning turbine turns the shaft in an electric generator, producing electricity.
Hydroelectric facilities are designed to match the water resource to be harnessed, thus, their size can vary. Because they are expensive, however, it often makes more sense to make them large, with greater than 100 MW output being common.
- Upfront Costs – Like nuclear generation, the bulk of the expense for hydroelectric projects comes from their initial construction costs (especially making the dam). This high initial investment makes hydroelectric facilities cost around 2,000,000 per MW.
- Fuel Costs – Free!
- Flexibility on the grid – A wisely designed hydroelectric facility is built on a water course that flows all the time. It is typical, especially in Canada, that this flow can change seasonally, with spring time bringing the largest volumes (with summer bringing the smallest). Because it is as simple as diverting water into or around the penstock, hydroelectric facilities can change their output very rapidly, amongst the fastest of any electricity generation technology. There are limits, however, letting too much water through for too long can drain the headpond leading to a variety of issues.
- Capacity Factor - Due to seasonal changes in water flow, and the strategic withholding of water behind a dam (to let it through during peak periods), typical capacity factors are around 35% but can be very different.
- Environmental Impacts – No CO2 emissions, except what is released during construction and maintenance, which amounts to around 9 g / kWh. There are environmental disruptions to neighboring ecosystems and the river course, which need to be carefully considered before a project is implemented.