Party Walls

In the first two entries of this series (Part One | Part Two), we explored advanced controls for electrically heated buildings; combined heat and power systems; upgraded atmospheric boilers and ventilation systems. For the final installment of SWA’s Favorite Multifamily Retrofits, we’ll examine the ins-and-outs of stand-alone energy storage.

Energy Storage Systems
Large-scale energy storage systems have the potential to normalize the peaks and valleys of electric supply and demand in multifamily buildings, but until recently widespread adoption of the technology has been hindered by costs. SWA conducted research for NYSERDA to assess the feasibility of using batteries to store energy in multifamily buildings. Preliminary results indicated that batteries may be used for this purpose, with a possible payback period as short as two to five years. Additionally, utility companies and grid operators have incentivized the use of battery systems to off-set load on the electrical grid. Batteries are also being integrated into more complex systems with cogeneration, solar power, and emergency backup functions.

Demand Response
During periods of high demand, grid operators may ask customers to voluntarily reduce their energy consumption to reduce strain off the grid. This can be done by turning-off equipment such as lights, air conditioners, and pool pumps, or scaling back thermostat set points. Batteries can aid in demand response by discharging during an event, effectively becoming independent power-stations capable of supplying electricity to all or part of a building. In the case of ultra high-performance multifamily buildings using on-site battery storage combined with renewable-energy sources, solar energy stored during the midday generating peak can be used to offset electrical draw during the evening demand peak.

Peak Demand Shaving & Load Shifting
For some buildings, demand charges may make up 40–60% of the electric bill, amounting to a major expense. Batteries can help mitigate demand charges by shaving the peaks off a building’s electric profile, discharging during peak hours in order to lessen the building’s kilowatt draw. Peaks that would occur during periods of high demand are served by the battery system, which then recharges during periods of lower demand. While factoring in the effects of environmental conditions, operating procedures, and control methods, the ideal buildings for application exhibit peak-heavy load profiles commonly associated with chiller, cooling tower, or cooling pump equipment reading on a single electric meter.

Another way to use energy storage is to take advantage of changes in electricity prices. By storing energy when it is cheap and discharging when it is expensive, an energy storage system can reduce the elasticity of market price. Some buildings can participate in day-ahead pricing, in which the utility publishes its predicted rates for the next day, and the customer adjusts its usage accordingly. Ten Barclay Street, a 58-story multifamily building in downtown Manhattan, installed a system with 1,000 kWh operating storage capacity in its basement, yielding roughly $80,000 in annual savings through a combination of peak load management, demand response, day-ahead pricing management, and standby electric rates. To maximize energy cost savings from day-ahead pricing, it’s essential to first determine proper building categorization according to Con Edison electric rate service classifications.

Considerations for Application of Batteries
Deciding where to place battery clusters can be challenging, as the tonnage is often so great that they must be installed in structurally reinforced areas or on the ground floor only. Factors such as system size, battery chemistry, and building construction all dictate range of placement options. Local fire codes may limit use of certain kinds of batteries, though most energy storage companies have access to a variety of battery types as a work around, e.g., lithium-ion, lead acid. Despite the learning curve associated with adaption of an emerging technology, energy storage systems are becoming increasingly accessible to a range of multifamily buildings types, and the need for such systems continues to rise congruently with the complexity of America’s energy landscape. Large buildings may be able to make use of energy storage capabilities for demand response or peak shaving. Buildings that use renewable energy may find storage systems to be a complementary technology, especially when emergency backup is needed. Market behavior indicates that battery energy storage technology for multifamily buildings is trending in a favorable direction, though there is still distance to cover before technology and market equalize and mainstream.

For more on this topic, read the article by SWA’s Marc Zuluaga and Sean Maxwell in the September/October 2015 edition of Home Energy Magazine.