Simple system calculation

A simple evaluation procedure can help to determine if solar water heating is appropriate. Traditional solar hot water heating systems are most cost effective in facilities with:

• Constant water heating load throughout the week and year; housing units and dining facilities
  are good candidates.
• High fuel costs to heat water; this is area specific.
• Sunny climates (which helps, but is not required); this is area specific.

The economic viability of a solar system depends on:

• amount of annual sunshine
• heating energy requirements throughout the year
• cost of the solar system
• price of conventional fuels (are the utility rates high in your area?)
• financing and incentives available (for 3rd party investors)
• what temperature of hot water is required (e.g., swimming pool vs. laundry)
• annual operation and maintenance costs.

The step-by-step method listed in Table 4.1 can be used to estimate the solar system size and its cost effectiveness. Table 4.2 lists general data for water heating loads for building types, solar resource, etc. Numbers are included for a sample building in Denver, CO and assume that the building uses electricity to heat water. The sample building group is four barracks, each housing 120 soldiers for a total of 480 soldiers. With a hot water use rate of 30 gal (114 L)/day/person, the hot water use would be 14,400 gal (54,000 L)/day. The heating energy to make this hot water is: