Balance of Power
A Warming Climate Could Affect Electricity
Thomas D. Veselka

How weather and climate affect electricity production
Weather and climate affect all types of electrical production — everything from traditional coal-fired power plants to those that run off renewable energies such as hydroelectric power or wind — but not in the same way.

Thermal plants — which use heat from burning fossil fuels and biomass, geothermal or nuclear energy sources to produce energy — account for about two-thirds of power generated in Western Electricity Coordinating Council (WECC). At thermal power plants, electricity generation becomes less efficient as the ambient air temperature increases. As a result, more fuel is consumed to produce the same amount of electricity, raising power plant emissions. This is most pronounced with technologies that use gas turbines, accounting for about 8 percent of the generating capacity in WECC. The amount of electricity a plant can produce also decreases when temperatures rise, which ultimately may require constructing more generating units. Furthermore, changing temperatures and humidity levels alter the effectiveness of power plant cooling systems, which are utilized by technologies that use steam as a primary mover; in this way, higher temperatures and more humid air, for example, can decrease the electricity-generation capacity of a plant.

Weather and climate also affect renewable power technologies — especially hydropower. Currently, renewable technologies produce about one-third of the electricity in WECC. The vast majority, about 85 percent, comes from hydropower plants that rely on water released from reservoirs or uncontrolled stream flows as an energy source. Factors such as precipitation, snowpack levels and the timing of snowmelt affect hydropower production. Moreover, humidity levels and wind speed impact water loss in reservoirs due to evaporation. The seasonal timing of precipitation and weather events significantly influences hydropower economics and the operation of the entire power system.

Electricity generated from hydropower plants has the highest value when the demand for power is the greatest. In most of the West, this typically occurs during the warmest summer months. But a warmer climate might mean earlier snowmelt, which could reduce the value of hydropower resources. Some of the negative impacts of early snowmelt can be mitigated through reservoir management, but there is a limit to the amount of water that can be stored. And hydropower plants that rely on river flows instead of reservoirs cannot store any water, so generation is dictated entirely by streamflow rates.

© Michael Collier; courtesy of ESW Image Bank

Glen Canyon Dam is one of the largest concrete dams in the world.

Other renewable technologies are also affected by weather and climate. Solar technologies, for example, are affected by cloud cover and the amount of solar radiation that reaches the ground. Wind power production can change drastically if wind conditions change. If the wind is too slow, power generation ceases. If the wind is too fast, wind turbines must be turned off to protect the equipment from mechanical and electrical stress. No one can predict what wind changes might occur with climate change, but it is important to note that any changes do affect the system.

Electricity generation is not the only facet of the electric grid system that is affected. Higher air temperatures exacerbate thermal expansion of power transmission and distribution lines, which cause lines to sag: Go outside on a hot summer day and you’ll notice that the electrical lines sag more than they do on a cooler day. That line sagging decreases the amount of power that can be securely transported. Other factors, such as wind speed and direction, also affect transmission line cooling. Under high load periods, the reduced capability of transmission lines increases congestion problems in some regions, potentially causing everything from utilizing units that have high operating costs more frequently to higher incidences of rolling blackouts.