NREL developed and applied a systematic approach to review literature on life cycle assessments of concentrating solar power (CSP) systems.
NREL developed and applied a systematic approach to review literature on life cycle assessments of concentrating solar power (CSP) systems, identify primary sources of variability between these assessments, and, where possible, reduce variability in greenhouse gas (GHG) emissions estimates.
Figure 1 summarizes the life cycle stages (based on harmonized data) for utility-scale CSP systems.
The harmonization for CSP technologies was done by adjusting published greenhouse gas estimates based on consistent application of:
- Four CSP system performance parameters: Solar fraction, direct normal irradiance, solar-to-electric efficiency and operating lifetime
- System boundary, for trough systems only by addition of auxiliary consumption of natural gas and electricity processes in the ongoing operational phase
- Global warming potentials (GWP) (based on IPCC 2007)
The table below summarizes the range of published values, harmonized value, and the impact on central tendency and variability of GHG estimates for each harmonization parameter. The central tendency is characterized by the median value. Variability is characterized by the interquartile range (75th minus 25th percentile values) and total range.
Figure 2 compares the published and harmonized life cycle GHG emissions for CSP technologies. Harmonization reduced the variability of published trough technologies by 69% and by 26% for tower technologies. The harmonization parameters that are most effective in reducing variability in the published life cycle GHG emissions estimates are solar fraction for trough CSP and operating lifetime for tower CSP.
The harmonized median life cycle GHG emission estimates for tower and dish technologies are similar but somewhat lower than those for trough technologies: 46, 25, and 13 g CO2eq/kWh, respectively.
Impact of Harmonization on CSP GHG Emissions Estimates1
|Harmonization Parameter||Range of Values||Harmonized Value||Impact on GHG Emissions Estimates|
|Solar Fraction (%)||75-100%||100%||Reduced 10%||Reduced 11%||Reduced 65%|
Irradiance (DNI) (kWh/m2/yr)
|1,914-2,865||2,400||Increased 9%||Increased 10%||Reduced 3%|
|20-40||30||Increased 6%||Reduced 15%||No change|
|Increased 6%||Reduced 12%||Reduced 3%|
|System Boundary Adjustment||—||—||—|