Advanced Energy Perspectives

The building envelope consists of all the elements of a building that separate its interior from the exterior environment: external walls, insulation, windows, and roofing. Advanced building envelope materials can reduce building energy use and costs by lowering heating and cooling loads, which account for roughly 50% of energy consumed by a typical U.S. home and 40% in commercial buildings. Heating and cooling loads can be reduced by as much as 40% simply by using efficient building envelope technologies. Roof and attic insulation alone can reduce heating and cooling needs by 10% to 15%.

There are two types of currents that can be used when transmitting electricity: Alternating Current (AC) and Direct Current (DC). The electric grid originally developed around AC power because it was easier to manipulate and transport ef ciently over long distances compared to DC power. Technological advancements have now made high voltage DC (HVDC) lines a viable option for long distance transmission. With HVDC, converters draw AC power from the grid and convert it to DC power. The DC power flows over the transmission line, then goes through a second conversion back into AC power before it is injected into the grid. Converters at both ends allow HVDC lines to transfer power between regional grid interconnections without disruption.*

A microgrid is a network of connected electricity generation assets, controls, and loads that can operate independently from a utility grid and/or easily connect to or disconnect from a utility grid. Microgrids usually range in capacity from less than 1 MW to 40 MW, and can generally be classified as customer microgrids, utility or community microgrids, or remote microgrids. Virtual microgrids link distributed generation (DG) at multiple sites. Remote and customer-owned microgrids are well-established applications, while utility, community, and virtual microgrids are emerging alongside intelligent grid technologies. In all cases, microgrids can generate, distribute, and regulate the flow of electricity to consumers at a local level.

Image courtesy of Ford Motor Company.

Hybrid electric vehicles (HEVs), commonly called “hybrids,” are powered by a combination of a conventional internal combustion engine (typically gasoline-fueled) and a battery-powered electric motor, usually featuring a nickel-metal hydride or lithium-ion battery. The hybrid drivetrain works in several ways to improve fuel economy. Having a larger battery than a conventional vehicle allows the engine to turn off at low speeds, when driving downhill, and while idling. Since the electric motor can assist with acceleration, a smaller gasoline engine is used, which reduces fuel consumption. The integrated system also allows the gasoline engine to operate in a more efficient power range.

Combined Heat and Power (CHP), also known as cogeneration, produces electricity and useful heat from the same fuel source in an integrated system. CHP systems recover exhaust or waste heat from electricity generation for use in industrial processes, space heating, and water heating. CHP technology achieves greater levels of overall efficiency than using separate thermal and power systems. Any fuel type can be used, including fossil fuels and renewable fuels. Because thermal energy (steam, hot water) is more difficult to transport than electricity, CHP systems are typically installed at sites with large, steady thermal loads, such as industrial facilities, college campuses, hospitals, and military bases. CHP systems can also power district energy plants, which produce steam, hot water, and/or chilled water at central plants, then distribute the steam or water to multiple buildings through a network of insulated pipes generally located underground.