Onsite Energy Technologies | Better Buildings Initiative

Onsite energy refers to electric and thermal energy generation and storage technologies that are physically located at a facility and provide clean energy services directly to the site. Onsite energy can encompass a broad range of technologies suitable for deployment at industrial facilities and other large energy users, including battery storage, combined heat and power (CHP), district energy, fuel cells, geothermal, industrial heat pumps, renewable fuels, solar photovoltaics (PV), solar thermal, thermal storage, waste heat to power (WHP), wind power, and others. Integration of multiple technologies can be used to meet decarbonization, resilience, and financial goals.

Battery Storage

Battery storage technologies allow electricity to be stored onsite and used on-demand. Onsite battery storage systems are used for demand reduction, energy price arbitrage, time shifting electricity from variable renewable resources, and instantaneous transitions for grid connection. Lithium-ion batteries are currently the dominant battery storage technology implemented across all sectors, although emerging technologies like redox flow and sodium sulfur batteries could become prominent. Battery storage systems require energy management software, relying on algorithms and computerized control systems, to seamlessly switch between charging the battery, extracting energy from the battery, and using grid power.

Energy Storage – Office of Electricity
Energy Storage Grand Challenge – Department of Energy

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Combined Heat and Power

Combined heat and power (CHP), also known as cogeneration, produces both electricity and thermal energy onsite in a single energy-efficient process. CHP can replace or supplement electricity provided from a local utility and fuel used in an onsite boiler or furnace. CHP systems are often categorized based on the type of prime mover that drives the system, including reciprocating engines, gas turbines, microturbines, fuel cells, and steam turbines. CHP systems can operate on various fuels—including natural gas, biogas, renewable natural gas (RNG), and hydrogen. CHP is ideal for sites that have consistent thermal and electric loads. Examples include chemical plants, pulp and paper mills, wastewater treatment facilities, food processing sites, hospitals, nursing homes, hotels, universities, correctional facilities, and multifamily buildings.

CHP Technology Fact Sheets
CHP Deployment Resources
CHP and Microgrid Installation Databases
CHP Project Profiles Database
CHP Basics – Industrial Efficiency & Decarbonization Office

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District Energy

District energy systems are characterized by one or more central plants producing hot water, steam, and/or chilled water, which are distributed through a network of insulated pipes to provide hot water, space heating, and/or air conditioning for nearby buildings. District energy systems serve a variety of end-use markets, including downtowns (central business districts), college and university campuses, hospitals and healthcare facilities, airports, military bases, and industrial complexes. By combining buildings and loads, district energy systems create economies of scale that enable the use of additional clean energy technologies. Combining a number of diverse load profiles allows the central energy plant equipment to operate at high load factors, resulting in higher levels of efficiency. New and different configurations of district energy systems are emerging in universities and communities all over the United States, including geothermal heating and cooling using ambient temperature water loops and a series of networked heat pumps.

District Energy Systems Overview – Industrial Efficiency & Decarbonization Office

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Fuel Cells

Fuel cells use electrochemical processes to convert hydrogen fuel into electricity. Through use of a fuel reformer, natural gas, biogas, propane, and methanol can also be used as fuels. In a fuel cell, a catalyst at the anode separates hydrogen molecules into protons and electrons, which take different paths to the cathode. The electrons travel through an external circuit, creating a flow of electricity. The protons migrate through the electrolyte to the cathode, where they unite with oxygen and the electrons to produce water and heat. Fuel cells can operate at higher efficiencies than combustion engines and have lower or zero emissions compared to combustion engines. Fuel cells operating on hydrogen emit only water, addressing critical climate challenges as there are no carbon dioxide emissions.

Fuel Cells – Hydrogen and Fuel Cells Technologies Office

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Geothermal

Geothermal energy is heat energy stemming from the earth’s core. Wells, ranging from a few feet to several miles deep, can be drilled into underground reservoirs to tap steam and very hot water that can be brought to the surface for use in a variety of applications, including electricity generation, direct use, and heating and cooling for residential, commercial, and industrial applications. The benefits of geothermal energy include its baseload 24/7 operational capabilities and its lack of greenhouse gas emissions. Natural geothermal reservoirs are primarily located in the western states of the United States, Alaska, and Hawaii. However, geothermal energy can be tapped almost anywhere with geothermal heat pumps and direct-use applications. The thermal energy storage properties of underground rocks and soils allow geothermal heat pumps to act as a heat sink—absorbing excess heat during summer, when surface temperatures are relatively higher—and as a heat source during the winter, when surface temperatures are lower.

Geothermal Basics – Geothermal Technologies Office
Geothermal Heat Pumps – Geothermal Technologies Office

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Industrial Heat Pumps

Industrial heat pumps are a class of active heat-recovery equipment that enables the re-use of process energy for space heating, hot water, and other applications, by increasing the temperature of a waste-heat stream to a higher, more useful temperature. Heat pumps can facilitate energy savings when conventional passive-heat recovery is not possible. Under the right circumstances, a heat pump can reduce energy costs, particularly when: 1) the heat output is at a temperature where it can replace a purchased energy source, such as boiler steam or fuel-fired process heat, and 2) the cost of energy to operate the heat pump is less than the value of the energy saved. The most common types of industrial heat pumps include closed-cycle mechanical heat pumps, open-cycle mechanical vapor compression heat pumps, open-cycle thermocompression heat pumps, and closed-cycle absorption heat pumps.

Electrification of U.S. Manufacturing with Industrial Heat Pumps – Lawrence Berkely National Lab
Industrial Heat Shot – Office of Energy Efficiency and Renewable Energy

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Renewable Fuels

Fuel sources considered renewable include biodiesel, ethanol, hydrogen, biogas, renewable natural gas (RNG), and renewable diesel. Biodiesel can be manufactured from vegetable oils, animal fats, or recycled restaurant grease for use in diesel vehicles equipment. Ethanol is made from corn and other plant materials. Hydrogen, when used in an onsite generator to provide electricity, is a zero emissions alternative fuel produced from diverse energy sources. Biogas is methane-rich gas formed from anaerobic digestion at farms, wastewater treatment plants, and landfills. RNG is essentially biogas (the gaseous product of the decomposition of organic matter) that has been processed to purity standards. RNG is a pipeline-quality gas that is fully interchangeable with conventional natural gas. Renewable diesel is a fuel made from fats and oils, such as soybean oil or canola oil, and is processed to be chemically the same as petroleum diesel.

Hydrogen Program – Department of Energy
Bioenergy Basics – Bioenergy Technologies Office
Renewable Natural Gas – U.S. Environmental Protection Agency

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Solar Photovoltaics

Solar photovoltaic (PV) modules, comprised of individual solar PV cells, convert photons from sunlight into electrical energy. These modules are connected to form arrays which make up a solar PV system. Solar PV systems can be installed on roofs, facades, or ground-mounted structures. They can have fixed orientations or use single axis (east-west) or dual axis (east-west and north-south) tracking systems programmed to follow the sun and achieve optimal tilt and orientation conditions at all times. The electricity production of a solar PV system depends on various factors including but not limited to the rated efficiency of the solar modules, the orientation and tilt of the solar installation, solar irradiation levels, temperature and weather conditions, shading, the type of installation (tracking system or fixed mounted), etc. While solar PV systems are suited for most locations, the highest levels of solar irradiance for most optimal solar PV production are found within the southwestern states of the United States and in southern Florida and Hawaii.

Solar Photovoltaic Panels for Industrial Applications Fact Sheet
Solar Photovoltaic Technology Basics – Solar Energy Technologies Office
Solar Energy Research Areas – Solar Energy Technologies Office

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Solar Thermal

Concentrating solar-thermal power (CSP) technologies use mirrors to reflect and concentrate sunlight onto a receiver. The energy from the concentrated sunlight heats a high temperature fluid in the receiver. This heat—also known as thermal energy—can be used to spin a turbine or power an engine to generate electricity. CSP systems can be in the form of parabolic troughs, linear Fresnel, power towers and dish-Stirling collectors. The sun’s resource is not always available, so thermal storage systems are typically implemented as a backup source of heat for thermal applications and electricity production. While CSP technologies are generally used at a utility-scale for generating electricity, solar thermal installations can also be used in residential, commercial, and industrial applications. For these applications, solar thermal collectors are installed on the roof of a building or as a ground-mounted system. The sun’s light energy heats up a glycol mixture, which is constantly pumped through the solar panels and routed through a heat exchanger to ultimately heat the water in various storage tanks. The hot water in those storage tanks can then be used for both hot water needs and space heating purposes.

Solar-Thermal Power Basics – Solar Energy Technologies Office
Solar-Thermal Power Research Areas – Solar Energy Technologies Office
Solar-Thermal Power and Industrial Processes Basics – Solar Energy Technologies Office

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Thermal Storage

Thermal energy storage (TES) technologies heat or cool a storage medium and, when needed, deliver the stored thermal energy to meet heating or cooling needs. TES systems are used in commercial buildings, industrial processes, combined heat and power (CHP) systems, and district energy installations to deliver stored thermal energy during peak demand periods. Thermal energy can be stored in various forms for cooling (collectively referred to as “Cool TES”) or stored as hot water for heating. A key driver for TES in general is the avoided capital investment in conventional (non-TES) chiller plant capacity. Several sensible TES technologies have been tested and implemented to capture the heat produced by, for example, concentrating solar-thermal power (CSP) systems. These include the two-tank direct system, two-tank indirect system, and single-tank thermocline system.

Thermal Energy Storage Overview – Industrial Efficiency & Decarbonization Office
Thermal Energy Storage – Building Technologies Office

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Waste Heat to Power

Waste heat to power (WHP) technologies produce electricity by capturing waste heat—typically from exhaust gas or industrial processes—and converting this waste heat to electricity. WHP is a clean energy technology; it produces no new emissions from the use of waste heat and often displaces electricity produced from carbon-based fuels.

WHP Technology Fact Sheet – Industrial Efficiency & Decarbonization Office

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Wind Power

Wind turbines use the wind’s kinetic energy to turn the propeller-like blades of a turbine around a rotor, spinning a generator, and generating electricity. Wind flow patterns and speeds vary greatly across the United States and are modified by bodies of water, vegetation, and differences in terrain. Wind turbines can be implemented both onshore and offshore. The Great Plains region of the United States contains the highest wind resource and potential for onshore wind installations.

Distributed Wind Energy for Industrial Applications Fact Sheet
Distributed Wind – Wind Energy Technologies Office
Wind Research and Development – Wind Energy Technologies Office

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