1. Our Friend, the Sun
Ethan Gottschalk

2. “Energy is the single most important challenge facing humanity today
“Energy is the single most important challenge facing humanity today.” – Richard Smalley, 2004.

3. Why Solar Energy?
Amount of energy striking the earth is variable, and numbers vary greatly with different units being utilized.
Total net energy = 1000 zettajoules.
Between 5 and 8 kwh striking surface of U.S. in June.
Total amount available is larger than all other forms of energy combined.

4. Different Ways to Use Solar Energy
Active Solar
Involves the collection of direct sunlight and the active movement of the trapped heat (using a pump,motor, or fan) for a specific purpose.
Active Solar Hot Water.
Active Solar Heating.

6. Photovoltaics (PV)
PV cells capture sunlight and transform it directly into electricity.
Present-day cells generate approximately one electron per photon received.
This amounts to conversion of about 20% of available sun energy into electricity.
New developments could increase this efficiency to 40%.

7. Benefits of Active Solar
Free fuel.
After initial production of materials, emissions are zero.
No noise.
PV units have no moving parts to replace and can be placed in modular units to move where needed.

8. Problems?
Active solar hot water and heating still require electricity to move heat.
Inefficiency.
Prohibitively expensive capital investment and maintenance.
Sun not always out: nighttime and cloudy conditions.
Energy Storage and transmission.

9. Passive Solar
Most often utilized in building design. Requires a knowledge of solar geometry.
Passive solar heating
Passive solar cooling

10. Passive Solar Heating
Direct Gain. Allows sun to directly heat the living space.
Indirect Gain. e.g. Trombe wall. Heat is collected and radiates through living space through convection, radiation etc.
Isolated Gain e.g. sunspace. Space is heated and can be closed or opened to rest of house.

11. Passive Solar Cooling Shading– Window awnings and overhangs.
Use of natural airflow.
Open windows at night to allow space to flush with cooler air and closing windows during day.
Exhausting of naturally-rising warm air.

12. Daylighting
Use of daylight for daytime lighting needs. (Rec Center at UM).
Clerestory windows and overhangs are a necessity so as not to cause overheating in the summer.

13. Benefits of Passive Solar
Affordable.
Energy-efficient and easy to maintain.
Zero emission.
The Ancestral Puebloan People couldn’t be wrong, could they?

14. Problems? Really?
What to do with existing structures that aren’t “passive-solar friendly”?
Far northern (and southern) latitudes may not see same benefits.
The weather.
In reality, there’s no good reason not to incorporate these building practices.

15. Steel-cage match: Will active or passive solar be victorious?
There’s probably not one right answer.
There’s really no reason to pit them against each other.
Utilizing both of them together looks like a good step, although solar is not a climate change/energy panacea at present.