Building Automation & Energy Conservation

possehastyMechanics

Nov 5, 2013 (3 years and 11 months ago)

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Solar Energy

Solar energy has been an under
-
achiever



renewable
sources
(non-nuclear)
8%
wind
0.5%
biomass
38%
hydroelectric
55 %
geothermal
5%
solar
1%
nuclear electric
8%
coal
22%
petroleum
39%
natural gas
23%
Source: U.S. Department of Energy

http://
symposium2011.serdp
-
estcp.org/Technical
-
Sessions/3C



2500+ years


Passive



take advantage of ambient conditions


250+ years


Active Loop



capture, store, & deliver thermal
energy


50+ years


Photovoltaics



convert sunlight into electricity


25+ years


Hybrid Systems

-

concentrating collectors &
others

Solar Energy Has A Long History

Passive solar collectors can be as simple as a
house designed to take advantage of daylighting.

Passive solar heating recognizes
the seasonal position of the sun.

Passive Day Lighting System


tracking dish to collect
sunlight


visible spectrum
transmitted using fiber
optics


packaged like a
fluorescent light


commercialization
underway by Oak
Ridge Lab

Active loops capture, store, and
distribute heat.

Subtle details influence energy
recovery for active loops

Photovoltaics capture, store,
and distribute electricity.

How does a photovoltaic cell work?

http://science.nasa.gov/headlines/y2002/solarcells.htm

Optimum Mounting Angle


Solar tracking systems improve overall efficiency up to
30% by keeping panels perpendicular to the sun.


A fixed panel set at the same angle as the latitude of the
site will receive the maximum annual solar radiation.


If the load demand is high in the winter (northern
hemisphere), set the panel tilt at latitude plus 15
°
.


If the load demand is higher in the summer (northern
hemisphere) set the array tilt angle at latitude minus 15
°
.

Solana 280 MW CSP plant in Arizona

3 square miles of mirrors

Solar Energy Influenced by:


atmospheric conditions


geographic location


time of day


pollution


season


Solar energy is impressive
on sunny days…

…but there’s not much solar
energy on cloudy days

Solar
energy
changes
seasonally

Sizing a Photovoltaic
Array

daily energy requirements (kW
-
hr)/day

Array Size in kW =

Electric Loads

How much solar energy
is available?

Average sunshine hours (hr/day)

Quantifying Home Electric Loads


Search using some of the following terms


Residential


Electric


Calculator


http://www.nhec.com/residential_energycalculators.php


h
ttp://www.tampaelectric.com/TEHMEnergySaversCalc.html

Web
-
Based PV Array Sizing


Combine the power of


Mapping programs


PV sizing algorithms


Satellite
-
based weather data


Databases of rebates, tax credits, and other
incentives


http://www.nrel.gov/eis/imby/


Solar energy challenges


Better methods of energy storage


Cheaper manufacturing methods


Better installation techniques


Higher efficiency

Is solar energy a viable option?

pro’s


free, renewable, and
non
-
polluting


provides day
-
lighting,
heat, & electricity


low maintenance


independence

con’s


more expensive than
conventional power


energy source
fluctuates

must evaluate
case
-
by
-
case