General Impact
The most direct impact efficient solar lighting has on the environment is the offset electrical demand primarily sourced from fossil fuels that powers lights. Cutting off this flow of GHG emitting electricity can have significant impact when implemented on a wide scale. Discerning the impact of a single light can help to make these calculations.
Quantifying Environmental Impact
Below is a guide to calculating the offset of carbon emissions of Soltech solar lights. The calculation uses our most popular light to date, the Sunlike 30W-200Lm/W solar luminaire which is powerful enough to be used on 20-foot-tall poles. What follows below are assumptions about the calculation and an excerpt from the United States Environmental Protection Agency site explaining about the key factor (7.07 × 10-4). When multiplied by the electrical demand, the national marginal emissions factor serves as the contemporary domestic benchmark for quantifying carbon pollution. After establishing this figure, the yearly carbon offset is then converted into a 10-year analysis.
The results: Every individual 30W Sunlike installed for 10 years is actively saving 134 pounds of carbon dioxide from contributing to the climate emergency.
Carbon Offset Calculation Assumptions:
-After 5 years of use, every light has 1 battery change which can take less than 5 minutes/pole.
-Only CO2 emissions are factored into the calculation for the offset of the electrical demand that would otherwise have a significant portion contributed to by non-renewable sources.
-This calculation includes transmission line losses.
EPA Excerpt:
Electricity Reductions (kilowatt-hours)
The Greenhouse Gas Equivalencies Calculator uses the Avoided Emissions and Generation Tool (AVERT) U.S. national weighted average CO2 marginal emission rate to convert reductions of kilowatt-hours into avoided units of carbon dioxide emissions.
Most users of the Equivalencies Calculator who seek equivalencies for electricity-related emissions want to know equivalencies for emissions reductions from energy efficiency (EE) or renewable energy (RE) programs. Calculating the emission impacts of EE and RE on the electricity grid requires estimating the amount of fossil-fired generation and emissions being displaced by EE and RE. A marginal emissions factor is the best representation to estimate which fossil-fired units EE/RE are displacing across the fossil fleet. EE and RE programs are not generally assumed to affect baseload power plants that run all the time, but rather marginal power plants that are brought online as necessary to meet demand. Therefore, AVERT provides a national marginal emissions factor for the Equivalencies Calculator.
Emission Factor
1,559lbs CO2/MWh*(4.536 × 10-4 MT/lb)*0.001 MWh/kWh = 7.07 × 10-4 MT CO2/kWh
Sources:
AVERT, U.S. national weighted average CO2 marginal emission rate, year 2017 data
EPA (2018) AVERT, U.S. national weighted average CO2 marginal emission rate, year 2017 data. U.S. Environmental Protection Agency, Washington, DC.
Annual Carbon Savings of 1 Sunlike 30W
30Watts*8 hours each night*365 days=87.6KWH of electrical needed per (1) year
Carbon CO2 emission offset=87.6 * emission Factor
87.6*7.07 × 10-4 metric tons
=0.0060802 metric tons
=13.4045464 pounds of CO2 saved by 1 Sunlike 30W each year.
If each of San Francisco’s 25,000 streetlights was a Sunlike 30W operating for (10) years:
=13.404*10(years)*25,000(lights)
This would save 3,351,136.6 pounds of CO2 every 10 years.
References:
https://www.epa.gov/energy/greenhouse-gases-equivalencies-calculator-calculations-and-references
https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions
https://www.sfwater.org/index.aspx?page=410
