Energy Storage for a Sustainable Development

Abstract

The CU Green, Palamanui Project Team worked to create an integrated document for the developers of Palamanui, a 725 acre community on the Big Island of Hawaii consisting of residential sections, a business park, town center, university, and hotel, regarding how the development can be more sustainable and environmental aware. The document addresses engineering issues, alongside architectural and environmental issues, including but not limited to solar generation, energy storage, plug in hybrid vehicles (PHEV), microgrids, smart architectural and landscape design, load management, waste water treatment, and the business aspects of each technology. The team worked together to combine engineering, environmental, social, architectural, and business aspects into a single overarching document recommending how the development can move towards sustainability. The following paper addresses the energy storage aspects for the Palamanui development, analyzing different technologies, operating scenarios, and financial results. Incorporating an energy-storage system in the Palamanui development is beneficial for all involved parties. Residents benefit from a more reliable grid, with increased distributed generation. The community and environment will benefit from increased solar generation and a reduction in required peak generation from HELCO, corresponding to a decrease in greenhouse gas emissions and pollutants. Lastly, the developers benefit because the property can be marketed as a sustainable development with a more reliable grid, thus increasing market value. The storage system can exist as a centralized plant, being a large battery bank or compressed-air-energy storage system (CAES), or the system can be distributed throughout the development as plug-in hybrid vehicles (PHEV) or individual home batteries. Of the many energy storage methods available, three are seriously considered for the Palamanui development: sodium sulfur battery banks, lead-acid battery banks, and small-scale CAES in fabricated vessels. Battery banks and CAES operate under the same concept, drawing energy from the grid during times of low demand (10 p.m. to 6 a.m.) or from excess solar generation. During times of peak demand, stored energy is discharged to the grid to meet daily loads. Of all the systems analyzed, the final recommendation is block storage distributed throughout the development using sodium-sulfur (NaS) batteries. Sodium-sulfur batteries are the most appealing because of the small footprint, long lifetime, and lower lifetime cost. CAES systems with natural-gas prove to be too expensive with Hawaii’s high natural-gas prices. CAES without natural-gas has potential, but with little to no commercial testing having been done on this systems, further investigation is required and strongly recommended.