Optimization of Utility-Scale PV Systems

Project developers, EPCs, utilities, financiers and other PV project stakeholders are relying on utility-scale photovoltaic systems for long-term energy production and profitability. These systems have proven to be viable sources of electricity as their power-producing capacity is realized.

However, PV system technology must continue to advance and decrease the cost of producing electricity in order for this trend to continue. Utility-scale PV systems must be optimized to provide maximum energy harvest at the lowest overall cost, while also minimizing risk to investors.

The following is based on the educational poster presented at Solar Power International by Ken Christianson, global product manager for SMA’s utility solutions group. The poster is available here for download.

Project lifecycle

The project lifecycle is a value chain that begins with system design and extends throughout the 20-plus year lifetime operation of the PV plant. Optimized inverter solutions bring value to every stage of the process and contribute to greater PV project profitability.

Next-generation PV systems must be flexible to accommodate large-scale plants in a variety of locations throughout the globe. Utility-scale inverters will maximize the degree of system integration so that fewer additional components are required.

The maximum integration of components simplifies planning and design while reducing balance-of-system costs by including things like an integrated control power transformer, housekeeping transformer for customer loads and a tracker supply transformer.

Many utility-scale systems are expanding energy harvest with higher DC-to-AC ratios, creating better time-of-day optimization and eliminating DC curtailment. As the DC-to-AC ratio increases, the time that the PV system delivers maximum power also increases, resulting in more energy production later in the day when electricity is most valuable. This leads to reduced system capital expenditures and greater system profitability.

Logistics

A complete DC-to-AC solution from one source reduces project management and logistical costs. The compact design of next-generation inverters, along with the optimal power block size, allows for a higher power density, which reduces transportation and shipping costs.

The two factors that have the greatest impact on the optimal block size are the inverter cost and DC homerun cost. The specific cost of an inverter will reduce to the point that the AC and DC switchgear have to be increased in size. At that point, the inverter specific cost increases exponentially.

DC homeruns increase linearly until the cable diameter increases to the point where the cable become difficult to work with, dramatically increasing construction and labor costs..

These factors make the ideal block size to optimize system costs between 1.9–2.2MVA globally.

Installation of commissioning

Optimized PV systems, featuring advanced inverter technology, benefit from increased construction velocity through reduced site work, installation labor and special equipment requirements. PV systems must enable fast, worry-free commissioning around the globe and meet any foreseeable grid connection requirements.

Incorporating the optimal block size for utility-scale systems reduces overall inverter units to transport to the site and commission, which also results in less inverter foundation pads to pour and other equipment to set.

Lifetime operation and maintenance

Meeting the needs of utilities and grid operators ensures consistent energy production without delays, contributing to overall system profitability. In addition, a high level of serviceability from an experienced partner that offers comprehensive O&M is critical to lifetime system optimization.

A comprehensively engineered solution suite with a maximum degree of system integration will optimize and secure the entire PV system for the life of the plant. Optimized solutions will minimize project risk during all stages: from the predictable and reliable speed to energization throughout the lifetime of the investment.