Chapter 6 part 2
Passive Solar Space Heating
Active Solar Space Heating
Thermal Energy Storage
Summary
Energy in the News
Direct Gain Space Heating
Why is thermal mass important? (Thermal time constant of building?)
Why did medieval lords live in stone castles? Are these best for dry or
wet climates?
Performance of a Passive Solar Building
What is the range of interior building temperatures? Range
Of outside temperatures? No auxiliary heat is used in this building,
Located in Concord, New Hampshire.
Trombe Wall
Heat stored within
Concrete wall
Vents closed at
Night.
Wall radiates heat.
Solar Greenhouse (Indirect Gain)
Can grow plants
In greenhouse.
Reduces air
Dryness in winter
Why?
Active Solar Hot Water System
What additional features are required in an active
Solar system compared to a conventional water heating
System? (European vs American hot water heating systems)
Hot Air Flat Plate System
Thermal mass provided
By rock bin.
Solar collector uses air,
not water. Hot air moved
By fan to rock bin or directly
To rooms of house.
Water preheated in rock bin.
Good for humid climate.
Not as efficient as water
Based solar system. Why?
Optimum Solar Collector Angle
Why does the
Optimum collector
Angle vary as a function
Of the season?
How Big Should a Solar Collector Be?
Q = I * epsilon * A
Where Q is the heat
I is the average solar insolation at the site
Epsilon is the efficiency of the solar collector
A is the surface area of the solar collector
Thermal Energy Storage
Q = m*c* delta T
Where Q is heat, m is mass, c is the specific heat
Of the substance and delta T is the change in temperature.
What is better for thermal energy storage, a substance
With a high specific heat or a substance with a low specific
Heat? Why?
How does mass affect the thermal energy storage of a
System?
Heat Capacity
Heat capacity = specific heat * density
Storing Energy in Phase Changes
Why are phase changes a very effective method of energy storage?
(think of changing water to steam)
Components of Solar Heating Systems
Solar Collector
Thermal Energy Storage
Distribution System
Active Systems: have pumps or fans