examples economics and eroei for conservation and solar power systems
TRANSCRIPT
Examples
Economics and EROEI for Conservation and Solar Power
Systems
Simplified Energy and Cost Analysis
For Low Flow Shower Heads Typical household can save 40% per
shower, or 9 gallons. Assume water temperature in is 70° F and heated to 120 ° F.
Energy Saved Per Day
If cost is 8.3¢/kWh, yearly savings are
Or $33/year
gal
lb
Btu
kWh
Flb
BtuFgal 3.8
3413
11)70120(9
kWhcyeardaysdaykWh 3.83601.1
daykWhESAVED 1.1
Cost of shower head ≈$15, replaced by homeowner at no cost
$ payback is
Cost of Saved Energy=
This is less than 1/10th the electricity
moyearmoYEAR
5.51233
15$$
TC
C
SAVED 0
kWh
C
yryrday
daykWh
C 05.0103601.1
1500
Cost of Conservation Example
Replace a standard A Lamp with a CFL Lamp.
A Lamp uses 75 Watts, $0.50CFL Lamp uses 20 Watts, $15Price of Electricity 8.4¢/kWhA Lamp life 8 months (2/3 yr)CFL Lamp life 10 years
Cost Difference in 10 years is:
50.7$8/1205.015$ monthlifemonth
Reduction in Energy Cost per year if lamp operates 3hr/day on 1,100hr/yr
yrkWWhr /1.5$/$084.055100,1
Reduction in equipment cost
Payback time
yr/75.0$yr/5.2$85.5/5.14$
Cost of Energy (simple)Energy Savings
Cost
Levelized cost (CCE)Effective discount rate, i =3%Life Time, t =10 yr
CRF
CCE
hrkWhrW /61100,155
kWcyrkW
yr/2.1
/61
/$75.0
tii )1(1 117.003.1103.0 10
kWhckWh 4.161117.05.7$
Parabolic Collector Analysis
Economics and Energy return oninvestment
Energy investment is equal to
The energy return is
EROEI is
Energy recovery is 1.5 years for a life of 15 years the EROEI is 10:1
yrBtu
yrBtu/%5.67100
1043.5
/1066.39
9
Btu91043.5
3 66 10 9. B tu yr
CO2 Generation
To compare the production of CO2 from the combustion of fossil fuels with the CO2 production from solar energy conversion systems, we will calculate the amount of CO2 that is added to the atmosphere per unit of energy produced by each system. We will illustrate the calculation procedure first for a fossil energy system using coal as fuel.
The basic stoichiometric equation for the combustion of coal is
energy released To calculate the amount of CO2 produced
per unit of energy generated we need to know the energy released per unit of carbon, i.e., the heating value, and the percent carbon content of coal.
C O C O 2 2
Both heating value and carbon content vary slightly among the types of coal used in the U.S.A. We will demonstrate the methodology using bituminous type coal which is plentiful and widely used for power generation. We are given a heating value of 29MJ/kg of coal and a carbon content of 40% by weight for bituminous coal.
With the data given, assuming complete combustion, one can obtain that the combustion of 1 kg of coal with 0.4 kg of carbon having a molecular weight of 12 yields 1.47 kg of CO2 while releasing 29 MJ of thermal energy.
If the conversion efficiency of the heat of combustion to useful energy is 70% we find that coal-fired energy systems will generate 0.0016 moles of CO2 per kJ of useful heat delivered