DC-Coupled Hybrid Projects Provide Higher Net Value When PV Penetration is High

Without storage deployment, the marginal grid value of PV is declining in markets globally

September 29, 2021


Solar photovoltaic (PV) power demand has increased due to favorable policies, technological advancements, cost reduction, and clean energy uptake. However, without storage deployment or an increase in price-responsive load, growth in PV capacity is accompanied by lower wholesale prices.

The lower prices, in turn, were leading to a decline in the marginal grid value of PV in markets globally.

Using a consistent framework, researchers from the Berkley Lab analyzed the net value of more than ten strategies to preserve the marginal grid value of PV with grid-friendly options. They explored techniques such as simple tilt and azimuth adjustments to vertical bifacial modules, provision of ancillary services, and addition of energy storage.

Empirical market data indicate the observed market value decline corresponds to expectations from previous models. PV developers have been shielded from this value erosion by long-term, fixed-price power-purchase agreements. However, in some markets, utilities and other PV power purchasers have found themselves buying a progressively less valuable product. The declining grid value of PV with higher penetration could limit the technology’s economic attractiveness and future demand.

The researchers said that while grid-friendly options can increase the grid value of PV, some can also increase costs. They opine that choosing between alternative configurations requires balancing value against costs to optimize net present value.

The team compared grid-friendly PV options with a base PV plant and similar underlying component costs in the same market. They claim this comparative approach avoids the complications of calculating absolute net present value, which is sensitive to fundamental dynamics affecting wholesale market prices, regional variation in market characteristics, and PV equipment costs.

Value and Cost of Grid-Friendly PV Options Relative to the Base PV Plant in California

The researchers found that established and emerging strategies designed to shift the timing of standalone PV generation at the expense of total generation, including orienting monofacial PV modules west or bifacial modules vertically, result in minor net-value benefits or penalties. They argue that adding energy storage to such systems magnifies the net-value loss because configurations that change the timing of PV production become redundant when the energy-shifting capabilities of storage are added. The largest net-value gains come from strategies that maximize generation in conjunction with storage, especially at high PV penetrations.

Under almost all the scenarios analyzed, the team found that a DC-coupled hybrid plant with a high inverter loading ratio and single-axis tracking provides the most net value when the PV penetration is high. The researchers claim this finding aligns with the growing commercial interest in hybrid solar plus storage plants.

According to a recent report by Berkeley Lab, PV system sizes continue to grow in the United States. In 2020, the median was 6.5 kW for residential systems, up from 2.4 kW in 2000. The median was 42 kW for non-residential systems in 2020.

Recently, the U.S. Department of Energy Solar Energy Technologies Office and the National Renewable Energy Laboratory stated that solar could account for as much as 40% of the nation’s electricity supply by 2035 and 45% by 2050.


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