Abstract of Proposed Work
Fossil power plants are the largest source of greenhouse gas emissions in the United
States. Through widespread use of better environmental controls, emissions of many harmful
airborne pollutants have been reduced over the past several decades. Still, the most costeffective
method for reducing emissions is burning less fuel by operating more efficiently. During
the hot summer months, many fossil plants end up burning more fuel due to a decrease in
efficiency brought on by higher than normal cooling water temperatures. A phase change
material (PCM) – based system to improve plant efficiency and reduce overall emissions is being
developed under a project funded by ARPA-E. This system is designed to remove heat from
cooling water through the melting of a PCM during the warm daytime. As the air temperature
falls during the night, the PCM is frozen in preparation for the following day. Several hydrated
salt PCMs are being investigated by Lehigh University, which can be melted and frozen at
between 25 and 30°C with a latent heat of approximately 170 J/g, and which are shown to not
degrade in heat storage capacity after decades of sustained use. Differential scanning calorimetry
(DSC) testing of CaCl2·6H2O-based hydrated salts has shown that they meet both the melt
temperature and latent heat requirements. These hydrated salts are known to be cost-effective,
are typically non-hazardous, and are widely available. 200 g samples of these salts have been
prepared and analyzed in a drop calorimeter to measure their melt temperature and latent heat
of melting. An automated cycling system has been constructed to melt and freeze (cycle) these
samples for up to 2,700 cycles. Since a single cycle represents a single day of system use (one day
and one night), 2,700 cycles represents over 7 years of continuous system operation. The
corrosion potential of construction materials options for the system are being evaluated through
exposure to the hydrated salts for time periods of up to one year. After completion of the cycling
and corrosion testing, a prototype PCM cooling system able to provide 1 kWh of cooling, will be
constructed of a material found to be suitable from the corrosion tests. Computational fluid
dynamics (CFD) modeling will be used in the development and optimization of the prototype. A
PCM shown to have sustained thermal performance (less than 10% reduction in latent heat of
melting) after 2,700 cycles will be used to fill the prototype. ARPA-E advances high potential,
high-impact energy technologies, with a focus on bringing products to market as quickly as
possible. After testing of the PCM prototype, it is expected that the project will continue with a
commercial demonstration of the technology, followed by commercialization by the project’s
lead, Advanced Cooling Technologies.
Fossil power plants are the largest source of greenhouse gas emissions in the United
States. Through widespread use of better environmental controls, emissions of many harmful
airborne pollutants have been reduced over the past several decades. Still, the most costeffective
method for reducing emissions is burning less fuel by operating more efficiently. During
the hot summer months, many fossil plants end up burning more fuel due to a decrease in
efficiency brought on by higher than normal cooling water temperatures. A phase change
material (PCM) – based system to improve plant efficiency and reduce overall emissions is being
developed under a project funded by ARPA-E. This system is designed to remove heat from
cooling water through the melting of a PCM during the warm daytime. As the air temperature
falls during the night, the PCM is frozen in preparation for the following day. Several hydrated
salt PCMs are being investigated by Lehigh University, which can be melted and frozen at
between 25 and 30°C with a latent heat of approximately 170 J/g, and which are shown to not
degrade in heat storage capacity after decades of sustained use. Differential scanning calorimetry
(DSC) testing of CaCl2·6H2O-based hydrated salts has shown that they meet both the melt
temperature and latent heat requirements. These hydrated salts are known to be cost-effective,
are typically non-hazardous, and are widely available. 200 g samples of these salts have been
prepared and analyzed in a drop calorimeter to measure their melt temperature and latent heat
of melting. An automated cycling system has been constructed to melt and freeze (cycle) these
samples for up to 2,700 cycles. Since a single cycle represents a single day of system use (one day
and one night), 2,700 cycles represents over 7 years of continuous system operation. The
corrosion potential of construction materials options for the system are being evaluated through
exposure to the hydrated salts for time periods of up to one year. After completion of the cycling
and corrosion testing, a prototype PCM cooling system able to provide 1 kWh of cooling, will be
constructed of a material found to be suitable from the corrosion tests. Computational fluid
dynamics (CFD) modeling will be used in the development and optimization of the prototype. A
PCM shown to have sustained thermal performance (less than 10% reduction in latent heat of
melting) after 2,700 cycles will be used to fill the prototype. ARPA-E advances high potential,
high-impact energy technologies, with a focus on bringing products to market as quickly as
possible. After testing of the PCM prototype, it is expected that the project will continue with a
commercial demonstration of the technology, followed by commercialization by the project’s
lead, Advanced Cooling Technologies.