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Harnessing Building Mass as a Thermal Energy Storage Medium

Imagine a typical high-rise office building in the middle of August. During the hottest point in the day, when energy demand is at its peak, the building’s power-hungry compressors are running at full throttle to maintain a comfortable temperature. All the while, building materials like concrete, drywall and steel are absorbing thermal energy, increasing the amount of time and energy required to achieve a comfortable ambient temperature for the building’s tenants.

But Clean Peak Energy’s patented technology is flipping this outdated approach to building operations on its head. By reducing the building temperature overnight and into the early morning, a building can take advantage of lower-cost, cleaner-burning energy sources. And then, by shutting down its power-hungry cooling systems during the day’s peak-use hours, the building’s overall energy consumption can be reduced by 10 percent or more, resulting in a 20 percent or greater savings in energy expense and up to a 30 percent reduction in peak energy demand. Yet, due to the building’s natural ability to store and slowly release thermal energy over time, occupants can expierience no change in their comfort.

How It Works

When a large building’s surface areas – largely concrete and drywall – are cooled by an additional 1- to 2-degrees, they store that thermal energy on multi-MW comparable scale. Then, that stored thermal energy slowly releases back into the building’s internal environment over time. Using an automated, scalable, energy-optimization system, the thermal mass of commercial office buildings, combined with their air-conditioning systems, can be harnessed in a controlled manner, allowing the building to serve as a thermal energy storage medium.

By raising its power demand moderately overnight and reducing its power requirement during peak-demand hours during the day, annual energy costs are reduced substantially, since peak-demand power costs commercial building operators more than off-peak power.

In addition, carbon emmissions are also slashed in the process, since supplemental, peak-demand is typically met by less-efficient sources with a larger carbon footprint.

Video: How Clean Peak Energy’s patented technology uses a building’s mass storing thermal energy, ultimately reducing energy costs and reducing carbon emissions.

Proprietary modeling utilizes building structure and mechanical data as well as building operations information to provide site-specific performance predictions. The system takes into account building structure and mechanical data and other building operations information to establish site-specific performance predictions. Then, optimization techniques are applied to determine the most economical operation of building HVAC systems each day.

Among the variables the system considers are hourly local weather, systems efficiencies, carbon emissions at the source and real-time electric market prices. The system is even capable of measuring the efficiency of a building’s chiller units, and operate just those which will result in the most effient use of energy to cool the building. The result of all of this data crunching and system fine-tuning is a substantial reduction in a large-building manager’s need to purchase energy during daytime peak hours at higher peak-rate prices. 

The performance and electric demand of building HVAC systems are analyzed, and then temperature setpoint strategies are set that shift HVAC electric consumption to take advantage of lower night-time/early morning temperatures and electric prices. By reducing the need for buildings to purchase energy during daytime peak hours at higher peak-rate prices, building operators can achieve 10% energy savings, 20% energy expense savings and up to 30% peak demand reduction.

The technology can be applied to any existing large building regardless of age, and requires no capital investment and no space requirement. Installation is simple and can be accomplished in less than two weeks.

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