Sun Helps Heat, Cool Dallas Station
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Drawing through courtesy of William Hidell, Architect
Staff Correspondent
The City of Dallas is now putting the sun to work to both heat and cool a recently completed fire station that is believed to be the first to use solar energy. The annual saving in energy cost is estimated at over $1100.
Located at Harvester Street and Irving Boulevard in sprawling Trinity Industrial Park northwest of downtown, the new Station 1 is a three-bay, onestory structure with 9000 square feet of floor space. Total building cost was $496,885. The site measures 180 by 238 feet. Presently housing only Engine 1, the station has quarters for 15 officers and fire fighters, plus the usual kitchen, lavatory, and office spaces, but no basement.
Mounted on the roof facing in a southerly direction are 60 17.2-squarefoot solar collectors on pipe columns supported by the steel joists which carry the roof structure over the 50 X 64-foot apparatus room. No special reinforcement was needed. Resting on insulation within each collector tray, beneath double panes of tempered glass, is a copper sheet containing integral water circulation tubes. Water flowing through these channels is warmed by the sun, exits at the upper end through flexible hose connections, then is stored at 150°F in a 2000-gallon, heavily insulated tank at ground level behind the building.
Hot water for heating
For winter heating, this hot water is pumped through air blower units throughout the station. It warms the apparatus floor via a network of pipes in the floor slab. Domestic hot water for cooking and washing is supplied from the same system, augmented by a 256,000-Btu gas-fired boiler.
For summer cooling, the total building air-conditioning load is 6 tons of refrigeration capacity (the apparatus room is not cooled). Half of this is supplied by absorption chillers which derive their operating power from the sun.
Station 1 is built to conserve energy. Windows are double-glazed and in the roof and ceiling above the apparatus floor is a total of 8 inches of fiberglass insulation. The walls, built around 4inch steel studs with an exterior brick facing, contain 4 1/2 inches of R-ll fiberglass. Circulating air ducts throughout the station are wrapped with a 2-inch, foil-faced, insulating blanket.
Amortization in 20 years
Total cost of the solar energy installation at Station 1 was about $81,000 (included in the overall building cost mentioned earlier). Current estimates are that this added cost will be fully paid off by fuel savings in less than 20 years.
As 1977 began, 1500 homes, schools, and commercial buildings nationwide were being heated (and sometimes cooled) by the sun. By September, the Energy Research and Development Administration (ERDA) had selected 20 commercial, individual, and university organizations to receive the first of millions of dollars in study grants to develop “simple, innovative solar heating and cooling systems.”
Dallas sought ERDA funding for its new station. But more than 300 proposals were submitted to the ERDA by mid-1976, from which 34 were picked to get the federal money. Dallas’ proposed did not make the grade, so the city decided to proceed on its own.
Reason for selection
Why was this building chosen as the city’s first venture into solar energy? According to Bill Burgesser, an architect with the Dallas Building Services Department, “The city was trying to get some solar work going. We already had an energy conservation program, because of the onset of the energy crisis a couple of years ago. The Texas Railroad Commission was warning us that the future fuel supply for building use would be limited.
City of Dallas photo
“A place which would be occupied all the time seemed a better candidate for a trial than an office building, with only daytime occupancy. So we picked this fire station, then in the design stages, as the place to try our solar.”
The initial cost comparison indicated a payback period of 22 years. More recent projections show a shorter period because the original” 10 percent assumed annual utility rate escalation now looks closer to 12 to 15 percent.
Maintenance costs comparable
What about maintenance costs of the solar equipment? Architect Randy Myers, who works with Burgesser, answered this way: “Upkeep on the equipment is about the same for either solar or conventional energy sources. The collectors do need to be washed off from time to time, but generally there is enough rainfall here to take care of that. If washing is required, there is somebody always at the station to do it, unlike other types of buildings having limited occupancy.”
An outside circular stairway gives easy access to the roof, where a hose bib is provided for collector washing—perhaps four or five times a year.
One of the more difficult problems in designing Station 1 was the lack of accurate local temperature data. Only area-wide weather statistics from the Fort Worth weather station were available.
Said Burgesser, “Most data is too general. There’s nothing on the ‘microclimate’ of our specific local area. We had to do the best we could, and it involved studying solar collector surface areas ranging from 930 to 1200 square feet.”
Heating and cooling load
A computerized procedure was used extensively to get final estimates for the building’s total heating and cooling load. Average heating needed was 2130 degree-days annually, ranging from a low of 0 for June through August to a high of 656 in January. The cooling load averaged 2518 degree-days per year, from 0 in January to 660 in July.
The Dallas climate does include some temperature extremes. The record low was 3 below on January 18,1930, and the record high was 111 on July 25,1954.
Normal sunshine over the city is 66 percent of the total possible. To best use that sunshine, the collectors are mounted at an angle to the rooftop carefully selected on the basis of the sun’s changing position throughout the year. Ideally, at the 32.5 degrees north latitude in Dallas, this angle should be 15 to 20 degrees for cooling, and 45 degrees for optimum heating. Many compromises resulted in the final choice of 17 degrees. Thought was given to having the collectors pivoted on axles so the angle could be changed for different seasons, but the extra cost did not appear to justify it. Station 1 was structurally designed by William Hidell, a Dallas architect, assisted by the local firm of Magill-Cloyd Mechanical & Electrical Consulting Engineers. The general contractor was the Collins Construction Co.
The station is similar to several others completed in Dallas during recent years. A second Dallas fire station has since been designed to accommodate the future installation of a solar system.
