The National Renewable Energy Laboratory's Guide to Solar Water Heating

D. Analysis Tools

Preliminary Screening To determine if your project is a possible candidate for solar hot water heating use Federal Renewable Energy Screening Assistant (FRESA) software. Developed by NREL, this Windows-based software tool screens federal renewable energy projects for economic feasibility. It is able to evaluate many renewable technologies including solar hot water, photovoltaics, and wind.

A somewhat more detailed screening tool is provided by the Canadian Retscreen.

Detailed Performance Once preliminary viability has been established, it will eventually be necessary to evaluate system performance to generate more precise engineering data and economic analysis. This can be accomplished based on hourly simulation software or by hand correlation methods based on the results of hourly simulations. For this task, consider using:

• FCHART, correlation method, available from the University of Wisconsin
• TRNSYS, software, available from the University of Wisconsin

E. Financing for Solar Water Heating

Alternate financing is available for solar hot water systems. Among the alternative financing mechanisms are Energy Savings Performance Contracting (ESPC) and utility programs including:

• DOE's Federal Energy Management Program (FEMP) has established an Indefinite Quantity Contract (IQC) under which any Federal agency can issue Delivery Orders for parabolic trough solar water heating systems in an ESPC arrangement. See FEMP's Solar Thermal Concentrating Super ESPC.
• Several utilities offer rebates, leases, or other solar water heating programs. A complete listing of incentives is provided in the Database of State Incentives for Renewable Energy. Check with your utility company.

Application

Consideration should be given to utilizing solar hot water heating systems on all projects where:

• the avoided cost of energy is high (gas not available, electricity rates above $0.034 per kWh),
• there is a dependable, consistent hot water requirement (such as enlisted quarters, laboratories, or hospitals)
• there is a reasonably high daily average solar radiation rate on a tilted surface (in excess of 4.5 kWh/sq. m./day), although if the avoided cost is high enough solar water heating is effective in most climates,
• energy security is important, such as on an international base where energy supplies could be interrupted.

For large facilities, active, indirect systems are most frequently used. For smaller facilities in mild climates with modest freeze threat, passive direct or indirect systems are also a viable option.

A Case Study

• Phoenix Federal Correctional Institution

RELEVANT CODES AND STANDARDS

The use of solar water heating is consistent with administration directives:

• Executive Order 13123, Section 403(h): "Agencies shall use off-grid generation systems, including solar hot water, solar electric, solar outdoor lighting, small wind turbines, fuel cells, and other off-grid alternatives, where such systems are life-cycle cost-effective and offer benefits including energy efficiency, pollution prevention, source energy reductions, avoided infrastructure costs, or expedited service."
• Executive Order 12902, Section 304: "The goal of the Federal government is to significantly increase the use of solar and other renewable energy resources."
• Energy Policy Act of 1992 (EPAct) directs agencies to:
  • "include renewable energy [such as solar water heating] along with energy efficiency measures" (Section 542 of the National Energy Conservation Policy Act),
  • "demonstrate new technologies, and include environmental benefits such as reduced greenhouse gas emissions in the criteria by which demonstration technologies are selected" (Section 549),
  • "include recommendations for cost-effective renewable energy projects" (Section 550).
• Energy Policy Act of 2005 (PDF 1.9 MB, 550 pgs)