National Renewable Energy Laboratory

Distributed Thermal Energy Technology

About the Project

NREL's Distributed Thermal Energy Technologies activities support NREL's Distributed Energy Program. It is funded through the U.S. Department of Energy's Distributed Energy Program under thermally activated technology research and development.

The Opportunity: Saving Energy and the Environment

Two-thirds of our natural resources that are burned to produce electricity (mostly coal and natural gas) are lost as heat to the environment. At NREL, we develop technologies that recover and recycle waste heat from onsite electricity production to power heating, cooling, and ventilation systems. As a result, indoor air quality is managed to enhance comfort and productivity, while providing a healthy building environment with the minimum amount of energy.

Air-conditioning systems driven by waste heat are energy efficient and environmentally benign. According to one estimate, desiccant dehumidification alone could reduce total residential electricity demand by as much as 25% in humid regions and save about 400 trillion Btu of energy each year in buildings in the United States. Desiccant dehumidification can also prevent emission of more than 24 million tons of carbon dioxide (CO₂) and provide a drier, more comfortable, and cleaner indoor environment with a lower energy bill. Thermally driven air-conditioning systems also displace chlorofluorcarbon-based cooling equipment, the emissions from which contribute to the depletion of the Earth's ozone layer.

Combined cooling, heating, and power (CHP) concepts that efficiently integrate distributed power generation with thermally activated technologies (TAT) reduce stress on the national electric grid by replacing peak-power-consuming HVAC components. These systems are better suited for controlling humidity and providing ventilation air in an energy-efficient manner.

Strategic Importance of TAT/CHP

An NREL researcher uses an advanced diagnostic technique that employs tracer gas to evaluate seal performance of a rotary HVAC component.

The Distributed Energy Program leads a number of ambitious and coordinated efforts aimed at promoting efficient use of national energy resources, reducing peak power demand on the grid, and providing a reliable and secure supply of energy to the country. The need for such a program is stressed by the recent energy crisis in California, the apparent vulnerability of centralized generation and transmission without storage capability exemplified by the Northeast blackout, and the projected growth of nationwide demand for energy.

Facilities with CHP systems recover waste heat from generators, turbines, or engines and use it for heating and cooling to maximize overall facility efficiency. TAT HVAC components can use these large quantities of low- to high-temperature heat to provide dry, cool, comfortable fresh air to building occupants.

Development and deployment of efficient and cost-effective TAT/CHP systems for buildings constitute important elements of the strategic plan for maximizing national energy savings and productivity gains. These systems offer unique capabilities for enhancing indoor air quality and comfort and are the best choice in many applications. In supermarkets, TAT humidity control is used to reduce the need for expensive, energy-consuming defrost cycles. Conventional vapor-compression cooling designs don't treat temperature and humidity loads separately. Consequently, oversized compressors are installed to dehumidify the incoming air. To meet humidity requirements, vapor-compression systems must be operated at low temperatures that reduce their efficiency and require reheating the saturated, cold air to achieve some degree of comfort. Both consequences are costly. Thermally driven air-conditioning systems, however, can supplement conventional air conditioners. By working together, they tackle the temperature and humidity loads separately and more efficiently. HVAC designers can then reduce compressor size and eliminate excess chiller capacity. Large-scale deployment of new power and HVAC systems not only requires lifting existing non-technical barriers, but also presents challenges to engineers and researchers for developing efficient and cost-effective components and optimum system configurations.

To further highlight the benefits of the distributed energy model at the national level, macro-analyses are required to evaluate and identify the opportunities and appropriate paths for technological advancements and deployment strategies as guidelines for industry leaders, policymakers, and end-users. This understanding of TAT/CHP's optimal role in the national energy scheme helps guide NREL's initiatives for field testing, parametric analysis, and component development in partnership with industry.

NREL's Research and Development Role

Through a dynamic and strategic approach in line with the DOE Distributed Energy vision, NREL's distributed thermal energy technology research is designed to meet the challenges surrounding efficient and cost-effective deployment of TAT/CHP systems for industrial, commercial, and residential applications. This research is conducted at NREL's world-class facilities in the Advanced Thermal Conversion Laboratory (PDF 911 KB) (Download Acrobat Reader). This work represents a collection of collaborative and synergistic activities that emphasize innovation, industry partnership, and visionary responsiveness to national and global needs. Components of the work include the following:

• Building the necessary knowledge base for promotion of optimal TAT/CHP systems by conducting analytical, experimental, and field studies.
• Disseminating technical information and guidelines for end-users and policy makers on the energy efficiency, environmental quality, and economic benefits possible through waste heat recycling.
• Identifying new technological advances and evaluating their roles in enhancing TAT/CHP systems.
• Assisting industry in eliminating technical and regulatory barriers.
• Developing advanced desiccant materials, components, and systems with lower costs and improved performance.
• Developing uniform test methods and performance benchmarks for TAT/CHP materials and dehumidifiers, adsorption sections, and whole systems to establish consumer confidence.
• Challenging prototype systems in real-world environments.
• Developing applications for TAT/CHP systems that highlight their abilities to improve indoor air quality and reduce environmental pollution.

The information and data generated through this collaboration is disseminated to the HVAC industry, thermally driven air-conditioning systems community, architects, engineers, builders, utilities, and other end users through industry and professional society meetings, publications, conferences, and workshops.

Because thermally driven air-conditioning systems perform differently than vapor-compression systems, performance-rating procedures, test methods, and standards are being developed to permit HVAC-system designers to compare these systems with competing technologies. Complementary procedures are being developed by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc., and the Air-Conditioning and Refrigeration Institute. Conventional comfort standards based primarily on temperature must be revised to include humidity and indoor air quality.

Technology advancements have improved the performance, reliability, and cost-effectiveness of thermally driven air-conditioning equipment. However, further cost reductions and improvements are needed before these systems can compete successfully in the broader residential and commercial buildings market. DOE is working with the U.S. Combined Heat & Power Association (USCHPA), The Energy Solutions Center, and other consortia to identify barriers to wider acceptance and propose research-backed solutions to these barriers.

Developing Strategic Goals with R&D Partners

An industry-coordinated program is critical to the success of TAT/CHP. In response, DOE develops and maintains technology roadmaps to coordinate its R&D with partners and stakeholders. In January 6-9, 2003, 53 practitioners from industry, government, universities, and national laboratories gathered for a TAT technology roadmap workshop. These partners included the Gas Technology Institute, gas utilities, desiccant dehumidifier equipment and manufacturers, enthalpy recovery ventilation manufacturers and HVAC equipment manufacturers, and more. Near-term goals focused on developing the next generation of thermally driven air-conditioning equipment for broader commercial applications. Long-term goals focused on developing second-generation, advanced systems for broad commercial and residential applications.

Major findings and conclusions from the TAT/CHP roapmap include the following:

• Thermally activated technologies are an important part of the Nation's strategy for accomplishing critical energy and environmental goals.
• There exists a renewable and pollution-free energy resource that thermally activated technologies are uniquely able to tap. Unfortunately, policy makers and energy developers are mostly unaware of this resource. Its potential for development is poorly understood. That resource is waste heat.
• Thermally activated technologies consist of equipment that use thermal energy for heating, cooling, humidity control, and power (mechanical and electric) in buildings, factories, campuses, industrial parks, and district systems. They include, for example, absorption chillers, desiccant humidity control, and organic rankine energy recovery devices. CHP systems are a major user of thermally activated technologies, systems in which TAT equipment is integrated with power generation equipment to generate energy savings for customers.
• TAT can be directly fired or operate using waste heat in CHP applications.
• Today's thermally activated product lines are largely focused upon burning of fossil fuels as their source of thermal energy. These current products reflect markets, end-use applications, and manufacturing capabilities that currently sustain profitable business operations. They produce measurable public benefits: higher energy efficiency, improved indoor air quality, lower air emissions, and lower peak demand for electricity.
• Needed are more efficient, reliable, and focused thermally activated technologies that are capable of operating using a variety of energy sources, including integration with low- temperature waste heat, CHP systems, clean fossil fuels, biomass, and eventually hydrogen.

Visit the USHPA for more information on the roadmap and related activities. Promotion of CHP and roadmapping efforts also take place at the regional levels. The Midwest CHP Application Center, the Intermountain CHP Application Center, the Mid-Atlantic CHP Application Center, and others coming online, are prime examples of local efforts.

Program Contacts

Patricia Hoffman

Program Manager
Distributed Energy Program
U.S. Department of Energy
EE-42, Room 5E-036
MS 6A-116
1000 Independence Avenue, SW
Washington, DC 20585-0121

Richard DeBlasio

Technology Manager
Distributed Energy Program
National Renewable Energy Laboratory
1617 Cole Blvd.
Golden, CO 80401-3305
303-275-4333

Steve Slayzak

Project Manager
Distributed Thermal Energy
National Renewable Energy Laboratory
1617 Cole Blvd.
Golden, CO 80401-3305
303-384-7527