Solar power costs keep falling, says US energy agency NREL…

16 Nov 2021

…while EPFL’s 3D chemistry breakthrough boosts perovskite efficiency to 23.9%.

The US National Renewable Energy Laboratory (NREL) has published its annual cost breakdown of installed solar photovoltaic (PV) and battery storage systems. The U.S. Solar Photovoltaic System and Energy Storage Cost Benchmark: Q1 2021 (report) details installed costs for PV systems as of the first quarter of 2021.

Costs continue to fall for residential, commercial rooftop, and utility-scale PV systems—by 3%, 11%, and 12%, respectively, compared to last year, says NREL. In a change from previous years’ reports, balance of systems costs have increased or remained flat across sectors this year. However, this increase in balance of systems cost was offset by a 19% reduction in module cost, causing overall costs to continue their decade-long decline.

The report’s authors used a bottom-up cost modeling approach that accounts for all system and project development costs incurred during installation to model the costs for residential, commercial, and utility-scale PV systems, with and without energy storage.

They also modeled typical installation techniques and business operations from an installed-cost perspective. NREL says that this strategy “ensures that hardware costs reflect the actual purchase price of components as well as the sales price paid to the installer, including profits”. The benchmarks assume a business environment unaffected by the novel coronavirus pandemic and represent national averages.

NREL’s solar and storage techno-economic analyst Vignesh Ramasamy commented, “As the costs of construction-related raw materials have increased during the pandemic, the total balance of systems material cost has either stayed relatively the same, or, in some cases, increased by a marginal percentage compared to the balance of systems cost reported in the Q1 2020 benchmark report.”

Storage costs also dropping

Starting with the 2020 PV benchmark report, NREL began including PV-plus-storage and standalone energy storage costs in its annual reports. The 2021 benchmark report finds continued cost declines across residential, commercial, and industrial PV-plus-storage systems, with the greatest cost declines for utility-scale systems (up to a 12.3% reduction).

A major component of total installed system costs is the cost of the PV modules. In a second report, Photovoltaic Module Technologies: 2020 Benchmark Costs and Technology Evolution Framework Results, NREL researchers calculate a minimum sustainable price (MSP)—the price necessary to support a sustainable business over the long term—for modules. Specifically, the report calculates that price by using bottom-up manufacturing cost analysis and applying a gross margin of 15%.

This report benchmarks three established, mass-produced PV technologies as well as two promising technologies that are currently under development or in pilot production. Crystalline silicon dominates the current PV market, and its MSPs are the lowest—$0.25–$0.27/W across the c-Si technologies analyzed.

Cadmium telluride modules have a slightly higher MSP ($0.28/W), and the copper indium gallium diselenide (CIGS) MSP takes a still bigger step up ($0.48/W), largely as a result of higher labor, equipment, and facility costs. The report provides technology road maps for additional MSP reductions. The prices of c-Si and CdTe modules remain similar to each other over the short and long term, whereas the CIGS premium shrinks, but the cost differential remains significant.

The two developing technologies the report considers are III-V and perovskite PV technologies. At $77/W, the III-V MSP benchmark is much higher than the benchmarks for established technologies, which has kept III-V PV technology in niche markets, such as space and terrestrial concentrator applications.

EPFL’s 3D chemistry boosts perovskite efficiency to 24%

An international collaboration led by chemical engineers at EPFL, Lausanne, Switzerland, has overcome a problem in the manufacturing of perovskites that reduces their efficiency as solar panels. The new approach produces perovskite solar panels with an efficiency of 23.9% and operational stability longer than 1000 hours.

Among the leading candidates for highly efficient and stable solar cells are lead iodide perovskites, which show excellent light-harvesting capabilities. However, their efficiency depends greatly on their manufacturing, and a key factor is removing defects from their light-harvesting surface.

The way this is typically done is with a method called “passivation”, which coats the surface of perovskite films with chemicals (alkylammonium halides) to make them more resistant and stable. The process adds a two-dimensional perovskite layer on top of the primary perovskite light absorber, which improves the stability of the device.

The problem is that passivation actually backfires by forming so-called “in-plane” perovskite layers that don’t “move” electrical charge as well, especially under heat. This is an obvious disadvantage for scaling up and commercializing potential solar panels.

3D chemistry to the rescue

In a new study, published in Nature Communications, scientists led by Mohammad Nazeeruddin at EPFL’s School of Basic Sciences, have found a way to solve the problem by treating them with different isomers of an iodide used to make perovskites. In chemistry, isomers are compounds that have the same molecular formulas but their atoms are arranged differently in three-dimensional space. The perovskite solar cells produced with this method showed an efficiency of 23.9% with operational stability beyond 1000 hours. The work also achieved a record efficiency of 21.4% for perovskite modules with an active area of 26 cm².