Transcript Energy Conservation - Trinity University

Solar Energy
Physics 1303
Three forms of solar energy.
Passive Solar
Active Solar
Photovoltaic
Passive Solar Energy
Sensible architectural design
Use sun in the winter
Avoid in the summer.
Cold climates- large glazing which
may be insulated at night and
opened during the day.
Hot climates - blocking the sun and
providing good ventilation.
Passive Design
Arizona Cliff
Dwelling is an
example of
traditional lowtech solution to
space heating and
cooling needs.
Passive Design
This is a modern New
Mexico version.
There is movable
isolation to put in
place at night.
Passive Design
Another interesting
design.
The wall is down and
the passive
collector is
collecting solar
energy
Passive Design
In this mode, the
wall is up and the
building is storing
solar energy or
blocking summer
heat gain.
An innovative passive design
Roof Pond House in
Atascadero,
California
Active Solar Energy
Use pumps and solar collectors to
provide energy.
Two types of solar collectors:
– flat plate
– concentrating
Flat Plate Collector
Made of a black absorbing plate with
water running through it or air
blowing past it.
Usually a flat plate collector has a
glazing to stop heat from escaping.
Efficiency 50% or better.
Flat Plate Collector
Hot Water Heater
Low cost heater in
the roof of this
modest Miami
house
Flat Plate Collector
Hot Water Heater
Low cost heater in
the roof of this
modest San
Antonio house
Flat Plate Collector
Hot Water Heater
 Solar water heater
system has four
components:
 Collector
 Tank
 Pump
 Controller
Flat Plate Collector
Flat Plate Collector
components:
 Plate with tubing
 Insulation
 Glazing
Concentrating Collector
A concentrating collector includes
some kind of lens or mirror.
Tracks the sun.
 High temperature.
 Efficiency near 50%.
Concentrating Collector
Components:
 Optics
 Glazing
 Absorber
 Insulation
 Tracking
Concentrating Collector
This one uses a
mirror and has no
glazing
Concentrating Collector
Used to be on the
roof of the Bell
center.
Concentrating Collector
This is the solar
concentrating
collector on the
CPS Headquarters
building on San
Pedro.
It runs the airconditioning
system
Flat Plat Collector Problem
Let’s work a problem
Solar Hot Water Heater
Flat Plate Collector Problem
A flat plate solar collector is used as a
solar hot water heater. The collector
area equals 20 square meters. The
collector is located in a location with
annual average daily solar insolation
equal to 5.0 kWh/square meter/day.
1.
Calculate the amount of solar energy
incident on this collector each day.
Solar Energy =
= 5.0 kWh / sq m / day • 20 sq m
= 100 kWh / day
2.
Assuming that the efficiency of the
solar collector and the rest of the
system equals 50%, calculate the
average daily energy produced (as hot
water) by this system.
Express your answer in kWh/day.
Average Produced Energy/day =
= 100 kWh / day • 0.50
= 50 kWh / day
3. Calculate the amount of energy
produced by this system each year.
Express your answer in kWh.
Annual Energy Production =
= 50 kWh/day • 365 day/year
= 18,000 kWh / year
4. Assuming that the solar energy
replaces the heating of hot water by
electric energy and that electric
energy cost 10¢/kWh, calculate the
yearly savings in electricity costs as a
result of using the solar hot water
system. Express your answer in
$/year.
Money Saved =
= 18,000 kWh • $0.10/kWh
= $1,800 / year
5. Suppose this solar hot water
system were to cost $5,400
(installed). Calculate the payback
period for this system
Payback = Cost / Savings
= $5,400 / $1,800 /year
= 3 years
Photovoltaics
Photovoltaic systems convert solar
energy directly into electricity. They
have efficiencies near 10%.
Photovoltaics
PV-powered airplane.
Is this really a good
idea?
Photovoltaics
PV arrays are widely
used for low power
loads.
Photovoltacis
A PV array is made
up of several
panels and a panel
is made up of
several cells.
Photovoltaics
A complete system
has an array, a
battery, an
inverter and a load.
The system can
supply either DC or
AC loads.
Photovoltaics
The inverter
converts the DC
voltage from the
PV array into an
AC signal to power
AC loads or to
connect to the
grid.
Photovoltaics
 Laurel Kaesler and
Frank Ehman
designed and built
the PV Project in
the Physics
Department
Photovoltaics
 The PV project has
4 components:
 Array
 Controller
 Battery
 Load
Photovoltaic
Controller
Photovoltaics
 The load is a pair
of fluorescent
lights that I use in
a small 3rd floor
lab in MMS
Photovoltaic
This is the solar
array on the CPS
Headquarters
building on San
Pedro.
Photovoltaic
 The output of the
array is inverted
into an AC voltage
and fed back to
the grid.
Photovoltaics
A high-tech solution
is to use PV to
capture sunlight as
electricity and use
the electricity to
produce
microwaves that
are beamed back
to earth.
PV Problem
Let’s work a PV
problem.
Photovoltaic Power System
PV Problem
A photovoltaic power system has a
collector area equals 100 square
meters. The collector is located in a
location with annual average daily
solar irradiance (insolation) equal to
5.0 kWh/square meter/day.
1. Calculate the amount of solar
energy incident on this collector each
day.
Solar Energy =
= 5.0 kWh / sq m / day • 100 sq m
= 500 kWh / day
2.
Assuming that the efficiency of
the PV array and the rest of the
system equals 10%, calculate the
average daily energy produced (as
electricity) by this system.
Express your answer in kWh/day.
Average Produced Energy/day =
= 500 kWh / day • 0.10
= 50 kWh / day
3. Calculate the amount of energy
produced by this PV system each
year. Express your answer in kWh.
Annual Energy Production =
= 50 kWh/day • 365 day/year
= 18,000 kWh / year
4. Assuming that the cost of electric
energy equals 10¢/kWh, calculate the
value of the electricity produced by
this system annually.
Value of energy or Savings =
= 18,000 kWh • $0.10/kWh
= $1,800 / year
5. Suppose this PV system were to
cost $27,000 (installed). Calculate the
payback period for this system.
Payback = Cost / Savings
= $27,000 / $1,800 /year
= 15 years
Solar Energy
Do you think solar
energy will able to
replace a
significant
fraction of the
energy needs of
our society?