Passive Solar Energy

Passive Solar EnergyBy: Jake WylieAndDustin Smith

DefinitionPassive Solar Energy: The use of solar energy through a collection, storage, and insulation process to produce heat energy.Insulation- for the purpose of keeping heat inside the structure and reducing loss of heatCollection of sunlight as heat- achieved through windows positioned on the South side of the structureStorage- Thermal mass is used to collect and store the energy from the sun (ex: water)

Pro’s of Passive SolarFairly expensive to build or install, but pays itself back pretty quickly.Probably the most environmentally friendly source of energy available to us today, as it creates no harmful effects. Changes in temperature occur slowly when the best thermal masses are used. This allows for heat energy to be conserved and used more effectively.

Our QuestionHow many gallons of water can be heated from tap temperature (55°F) to shower temperature (100°F) using only passive solar energy from a building similar to the Linfield greenhouse during one day from the hottest month of the year?How many showers will this translate into?

DataFirst we measured the size of the greenhouse which we found to be 640 ft.2.Received data from Dr. Heath that was found by using dual axis trackers which represent the maximum solar radiation at a site available. This data was compiled by the National Solar Radiation Database at their site in Portland.We found that the hottest month was July and used the data for that month: 8.6 KwH/M2 per day.

Data 2100°F = 37.78°C = 310.78K55°F = 12.78°C = 285.78K

Efficiency= 0.40 or 40% (a typical efficiency- found in our workshop 4 worksheet)Qto raise temp.= mass × c × ΔT

= (8.337lb / 1) × (1Btu / lb°F) × (45°F/1)= 375.165 Btu for 1 gal h2o

Data 3Insolation: (8.6KwH / m2) × (3413Btu / 1Kwh) × (1m2 / 10.76ft2) × (640ft.2 / 1) × (1gal h2o / 375.165Btu) = 4653.5 gal h2o/day.

(4653.5 gal h2o/day) × 0.40 (efficiency)

= 1861.4 gal h20/day.

Data 4Avg. shower uses 2.5 gal water per min.Avg. shower time is around 5 min. longTherefore, we use about 11 gal water per shower.

(1861.4 gal h20/day) × (1 shower/11 gal h2o)

= 169.2 showers/day

ResultsWe would be able to heat 1861.4 gallons of water to 100°F from 55°F using the passive solar energy from a building similar to the Linfield greenhouse during a day in July.We would also be able to use this heated water for the use of 169.2 showers.

LimitationsThe data used was from Portland, not McMinnvilleData will change from year to yearWe assumed no heat energy escaped the collection systemWe used the hottest month of the year. The data will change from month to month and even day to day.

ConclusionObviously, passive solar energy can be an extremely effective source of energy. It can save a lot of money in the long run, and is environmentally friendly.Future construction companies should consider and are beginning to use passive solar energy designs when building new structures and houses. Questions?

ReferencesRistinen, Robert A., and Jack J. Kraushaar. Energy and the Environment. 2nd ed. N.p.: John Wiley & Sons, Inc., 2006. N. pag. Print.Workshop 4 In-class worksheethttp://ceer.alfred.edu/news/news%20archives/nadworny%20dome.htmPhotovoltaics design and installation manual. British Columbia: New Society Publishers, 2004. N. pag. Print.