Earth

1
Earths Changing EnvironmentLecture 22

• Energy Conservation in Heating and Cooling

2
Space Heating
3
Space Heating

• The amount of heat that flows through a wall or
  window may be calculated by the following
  formula
• Heat Loss (Btu/hour)
• Wall Area (Tin - Tout) R-value
• R-value of insulation indicates its resistance to
  the flow of heat.
• R-20 has twice the resistance to heat loss as
  R-10.

4
How do we lower energy consumption for space
heating?

• Increase R-value of walls, ceiling, and windows.
• Increase efficiency of furnace.
• Use heat pump.
• Use natural gas rather than electric heater.
• Better home design and construction.
• Lower Tin. (Easy lifestyle change)
• Decrease wall size. (Major lifestyle change)

5
Insulation

• Increasing ceiling and wall insulation is the
  cheapest technique for reducing heating and
  cooling loads for a building.

6
Windows

• Double or triple pane windows have a much higher
  R-value than single pane windows.
• Low emissivity glass, heat absorbing glass, and
  reflective glass depending on climate.
• Using better insulated frames and casements and
  sealing leaks.

7
Furnace Efficiency

• Annualized Fuel Utilization Efficiency
• Older units have 50 or 60 values.
• Newer units have 80 efficiency.
• Payback period for new units is about a year.

8
Geothermal Heat Pump (GHP)Heating

• GHP is very efficient and can be used for heating
  and cooling.

9
Geothermal Heat Pump (GHP)Cooling

• Payback Period 2 to 10 years. High initial cost.

10
How do we lower energy consumption for
Air-Conditioning?

• Increase R-value of walls, ceiling, and windows.
• Increase efficiency of Air-Conditioner. Use heat
  pump.
• Better home design and construction.
• Raise Tin. (Easy lifestyle change)
• Decrease wall size. (Major lifestyle change)

11
Air-Conditioner Efficiency

• Regulated by the U.S. DOE.
• Efficiency rating -SEER (seasonal energy
  efficiency).
• SEER is defined as the annual cooling output
  (Btus) divided by its total energy input
  (Watt-hours) during the same period.

12
Air-Conditioner Efficiency - SEER

• The minimum SEER allowed for a central A/C is
  9.7.
• The best available SEER is 18.
• Older units have SEER ratings of 6 or less.
• Consumers should look for a SEER of 12 or higher
  when buying a new A/C system.

13
Air Conditioner Efficiency Calculation
14
Retrofit and Payback
Suppose an older home in San Antonio is equipped
with a central air-conditioning unit with SEER
rating equal to 6 and that this home consumes
36,000 kWh of electrical power each year to power
this system. Suppose this system is replaced by a
central unit with a SEER rating equal to 18.
15
1.  How much energy (in kWh) is consumed annually
by the central A/C unit after the upgrade?

• Energy Consumed
• 36,000 kWh Old SEER / New SEER
• 36,000 kWh 6 /18
• 36,000 kWh 1 /3
• 12,000 kWh

16
2.  How much energy is saved annually by
switching to the A/C unit with the higher SEER
rating?

• Energy Saved
• 36,000 kWh 12,000 kWh
• 24,000 kWh

17
3.  How much money is saved annually, assuming
that the cost of electricity equals 0.10/kWh?

• Money Saved
• 24,000 kWh 0.10/kWh
• 2,400

18
4.  What is the payback period if the cost of
purchasing and installing the new A/C unit equals
4,800?

• Cost 4,800
• Savings 2,400/year
• Payback Cost / Savings
• 2 years