Sustainable Building Technical Manual - Etn-presco.net

– Locate collectors to avoid blinding hazards from reflected sunlight. In addition toabsorbing the sun's energy, almost all collectors reflect light at certain angles. Thisreflection is undesirable when directed at the occupants of another building and canbe hazardous if directed toward a road or machine operator.❑ Design collectors to withstand all weather conditions.Heavy snow loads, ice storms, and especially hailstorms can damage collector glass.Tempered glass or reinforced glass is often used to increase resistance. Structures supportingcollectors have to be designed to survive wind loads from all directions. Astructural engineer should be consulted to ensure compliance with all structural codes.❑ Design and locate collectors to maintain a clean surface and facilitate cleaning.Dirt and dust on collector glazing can easily reduce system efficiency by 50 percent ormore. Insist upon a location and system materials that minimize dirt collection. A regularmaintenance schedule is aided by easy access to the collectors, a source of water,and a nearby drainage system. Very large, tall, or horizontal collectors may need to bedesigned to support the weight of maintenance personnel. In some cases, rainwatermay provide adequate surface cleaning.❑ Minimize heat losses from the system.– Minimize the distance from collection to the storage source. The longer the runfrom the collectors to storage, the greater the heat loss and reduced system efficiency.For solar heating, locate storage near the central heating system.– Optimize insulation of collectors, ducts, pipes, and storage. Greater insulationshould be installed for higher-temperature collection levels.– Place duct and piping runs within conditioned space. This design can be advantageousduring the heating season, but may be disadvantageous during the cooling season.❑ Avoid over-designing to ensure the longevity of an active solar system.– Minimize controls. Control technology, along with computer and sensor technology,has advanced significantly over the past years, making older versions quicklyobsolete. New systems provide higher efficiencies and greater returns on investment.In addition, the design and building management team should provide maintenancestaff with system controls training to optimize system operations.– Minimize maintenance. A system that is self-maintaining is likely to have a higherefficiency and lower failure rate, and thus the best economic payback. Generally,the fewer moving parts, the less maintenance required. Active solar space-heatingsystems generally are not operating year-round, so their moving parts must be reliableenough to work intermittently. Pressure-relief valves, self-cleaning surfaces,and overheating sensors pay for themselves by extending the life of the system.– Maximize access to collectors, pipes, ducts, and storage areas. Assume that all partsof a system may have to be maintained and replaced in the future, and make surethat maintenance and replacement will not be difficult. Pipes and ducts buriedin walls and under concrete slabs will be costly to fix, and thus are more likelyto be abandoned.A c t i ve Solar Hot Wat e r❑ Select the type of solar hot-water heater according to climate, cost, and operationsand maintenance preferences.There are five types of solar water-heating systems:– Thermosyphon Systems. These systems heat water or an antifreeze fluid, such asglycol. The fluid raises by natural convection from collectors to the storage tank,which is placed at a higher level. No pumps are required. In thermosyphon systemsfluid movement, and therefore heat transfer, increases with temperature,so these systems are most efficient in areas with high levels of solar radiation.– Direct-Circulation Systems. These systems pump water from storage to collectorsduring sunny hours. Freeze protection is obtained by recirculating hot water