Passive Solar EnergyBy: Jake WylieAndDustin Smith

Definition

Passive 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 heat

Collection of sunlight as heat- achieved through windows positioned on the South side of the structure

Storage- Thermal mass is used to collect and store the energy from the sun (ex: water)

Pro’s of Passive Solar

Fairly 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 Question

How 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?

Data

First 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 2

100°F = 37.78°C = 310.78K

55°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 3

Insolation:

(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 4

Avg. shower uses 2.5 gal water per min.

Avg. shower time is around 5 min. long

Therefore, we use about 11 gal water per shower.

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

= 169.2 showers/day

Results

We 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.

Limitations

The data used was from Portland, not McMinnville

Data will change from year to year

We assumed no heat energy escaped the collection system

We used the hottest month of the year. The data will change from month to month and even day to day.

Conclusion

Obviously, 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?

References

Ristinen, 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 worksheet

http://ceer.alfred.edu/news/news%20archives/nadworny%20dome.htm

Photovoltaics design and installation manual. British Columbia: New Society Publishers, 2004. N. pag. Print.