Searching for the Optimal Mix of Solar and Efficiency in Zero Net Energy Buildings
Zero net energy (ZNE) buildings employ efficiency to reduce energy consumption and solar technologies to produce as much energy on site as is consumed on an annual basis. Such buildings leverage utility grids and net-metering agreements to reduce solar system costs and maintenance requirements relative to off-grid photovoltaic (PV)-powered buildings with batteries. The BEopt software was developed to efficiently identify cost-optimal building designs using detailed hour-by-hour energy simulation programs to evaluate the user-selected options. A search technique identifies optimal and near-optimal building designs (based on energy-related costs) at various levels of energy savings along the path from a reference building to a ZNE design. In this paper, we describe results based on use of the BEopt software to develop cost-optimal paths to ZNE for various climates. Comparing the different cases shows optimal building design characteristics, percent energy savings and cash flows at key points along the path, including the point at which investments shift from building improvements to purchasing PV, and PV array sizes required to achieve ZNE. From optimizations using the BEopt software for a 2,000-ft{sup 2} house in 4 climates, we conclude that, relative to a code-compliant (IECC 2006) reference house, the following are achievable: (1) minimum cost point: 22 to 38% source energy savings and 15 to 24% annual cash flow savings; (2) PV start point: 40 to 49% source energy savings at 10 to 12% annual cash flow savings; (3) break-even point: 43 to 53% source energy savings at 0% annual cash flow savings; and (4) ZNE point: 100% source energy savings with 4.5 to 8.1 kW{sub DC} PV arrays and 76 to 169% increase in cash flow.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1022366
- Resource Relation:
- Conference: Proceedings of the Solar 2008 Conference, 3-8 May 2008, San Diego, California (CD-ROM); Including Proceedings of 37th ASES Annual Conference, Proceedings of 33rd National Passive Solar Conference, and Proceedings of the 3rd Renewable Energy Policy and Marketing Conference; Related Information: For preprint version see NREL/CP-550-42956
- Country of Publication:
- United States
- Language:
- English
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