Initial Empirical Results for the Energy Payback Time of Photovoltaic
Modules
This research contributes to the growing literature on net benefits of renewable
energy systems by conducting an empirical investigation of the energy requirements
and net energy production of as-manufactured photovoltaic modules, evaluating
both established and emerging products. Results are based on utility bills,
measured energy use, and production records. Crystalline silicon modules
achieve an energy break-even in a little over three years. The energy payback
time for thin film copper indium diselenide in full production is just under
two years. Over their lifetime, these solar panels generate nine to seventeen
times the energy required to produce them. Energy content findings are presented
for the major materials and process steps for both single-crystalline silicon
and thin film copper indium diselenide.
Energy Balances for Photovoltaic Modules: Status and Prospects
Recent work has demonstrated that photovoltaic modules are net energy producers.
Based on empirical analysis of utility bills and production records at Siemens
Solar Industries, energy payback time for crystalline silicon is on the
order of three years and for thin film copper indium diselenide ranges from
ten years in research mode to under two years in production. About half
of the energy content is process energy, half is embodied energy in incoming
raw materials. This paper explores the energy balance implications of ongoing
and longer-term development efforts. Future prospects for both crystalline
silicon and copper indium diselenide are discussed, including production
scale and yields, new processes and equipment, waste reduction and reclamation,
of existing equipment reconfiguration, and product design.
An Empirical Perspective on the Energy Payback Time for Photovoltaic
Modules
Energy payback time is the energy analog to financial payback, defined as
the time necessary for a photovoltaic panel to generate the energy equivalent
to that used to produce it. This research contributes to the growing literature
on net benefits of renewable energy systems by conducting an empirical investigation
of as-manufactured photovoltaic modules, evaluating both established and
emerging products.