The objective of this project was to demonstrate a solar power plant that achieves grid-parity solar power without tax credits or rebates on a Department of Defense (DoD) installation. In this project, grid-parity is defined as the solar power plant installed and operated at a cost at or below the cost of electricity provided by the local utility, including all energy and demand charges.
Specific objectives were to:
- Demonstrate that solar power can cost-effectively provide the energy security, reliability, and independence required for U.S. military installations while concurrently meeting our Federal renewable energy goals of 25% renewable by 2025 (EPAct and Executive Order 13423).
- Demonstrate that Nanosolar, a San Jose, California based manufacturer of solar cells and panels, could build such a solar power plant with low-cost solar cells manufactured in the United States.
- Design and build a Nanosolar power plant for $3.20/watt direct current (DC) fully-installed, or less than 11 cents/kWh (levelized cost of energy [LCOE]), thereby demonstrating a means for the DoD to stabilize increasing utility costs at installations nationwide with solar electricity.
- Create a set of standard solar power plant designs to enable the DoD to install solar power at installations nationwide at or near grid parity as measured by LCOE electricity costs.
Conventional solar cell manufacturing processes often utilize very expensive vacuum deposition and sputtering equipment in clean room environments, thus driving up costs for traditional panels. Nanosolar utilized an innovative nanotechnology to enable high-volume production of low-cost solar panels. Nanosolar “prints” a layer comprised of a nanoscaled structured suspension of copper, indium, gallium, and selenium (CIGS) onto aluminum metal foil with a slot-die coater. The printed material is dried in an oven before subsequent processing. After properly dried, the printed rolls are then transformed into an opto-electronically mature crystalline semiconductor through several roll-to-roll rapid thermal processes. Individual solar cells are spliced, measured, interconnected, and assembled into solar modules. The production process is highly automated in a non-clean room production setting using relatively standard equipment and processes with few modifications, which substantially lowers the cost of manufacturing panels.
In May of 2012, Nanosolar commissioned a 1MW thin-film, ground-mount solar photovoltaic (PV) power plant at Camp Roberts, California. Cost cutting features in the plant design included: (1) frameless solar panels manufactured with a unique, low-cost, printed CIGS technology; (2) larger 1,937mm x 1,034mm panels than current, typical panels resulting in a lower Balance of Systems (BoS) racking, cabling, and home run cost; and (3) under-grounded cable plant design. Testing and monitoring of the system ran for 12 months duration after plant connection to the grid and a short conditioning period during which the solar panels ramp to full energy generation capacity.
This project demonstrated that several key objectives could be met with respect to distributed generation, including achieving a LCOE of $0.115/kWh at an installed cost of $3.44/W. The table below provides a summary of the overall achievements for each performance objective—system economics, greenhouse gas emissions reduction, reliability, and user satisfaction. Due to the cessation of operations, the objective to develop a set of standard solar power plant designs for the DoD was not met.
Quantitative Performance Objectives
System Economics (LCOE).
$0.110/kWh real dollar LCOE. $3.20/W solar power plant cost.
Energy generated& performance degradation. Cost of solar plant design, construction and installation.
Energy produced is equal to or greater than simulated results. Cost of project at or under budget.
$0.115/kWh real dollar LCOE. $3.44/W solar power plant cost.
Greenhouse Gas Emissions Reduction.
309kg CO2/kWh savings (base-load output).
Energy produced by solar panels. CO2 emissions of alternative electricity generation methods.
Calculated savings is equal to or greater than expected results.
Calculated amount of CO2 saved is 783,420kg.
The amount of time the system is operating per design.
Uptime equals estimates.
Uptime 98.4% per data from Meteocontrol.
Photovoltaic Peak Capacity (Installed).
Installed capacity of panels.
Capacity of 1 MW DC.
Capacity = 998.4 kWp DC.
Photovoltaic Peak Capacity (Power Delivered).
PVSyst estimate, 1,638 MWh AC (Weather Adjusted).
Power delivered to Camp Roberts over the entire year.
Matches estimates with less than or equal to 3% degradation of power peak delivered.
Actual = 1650 MWh AC.
Renewable Energy Produced.
PVSyst estimate, 1,638 MWh AC(Weather Adjusted).
Energy produced over an entire year.
Matches or exceeds estimates from PVSyst.
Actual = 1650 MWh AC.
Months, number of panels replaced.
Cleaning and maintenance schedule.
Site maintained to specifications provided.
Complete.Replaced 9 panels due to infant mortality.
Dollar costs, photovoltaic capacity.
Less than $3.20/W DC.
Quantitative Performance Objectives
Degree of Satisfaction.
Stakeholder Interviews & survey.
Good results reported from demonstration project.
High degree of satisfaction reported from stakeholder interviews.
DoD military installations throughout the United States can benefit from competitive electricity costs through on-site, distributed solar generation. Similar projects ranging from 1 to 20MW could enable distributed power to be produced within existing distribution lines, which avoids expensive transmission step-ups and tie-ins. This range of power plant outputs could be readily constructed at DoD installations nationwide.
Nanosolar’s innovative printing technology allows for cheaper production of PV panels and lower BoS cost. These panels also have shorter construction and installation times than other thin film companies, particularly on sites where power-assist equipment can be utilized. This is because Nanosolar manufactures larger panels that require fewer mounting fixtures than their competitors.
Improvement opportunities identified for future projects include:
- During system construction, panel should be mounted higher from the ground for easier maintenance and to prevent damage while the power plant is in operation.
- Operations and maintenance cost reductions could be achieved by modifying the system to allow use of livestock (e.g. sheep) to prevent buildup of grass and weeds under and around panels.
- Design teams should consider variations in panel mounting angle to optimize energy yield for peak summer loads when the solar PV power plant offsets expensive utility electricity cost.
- Primary drivers of BoS costs are changing. Panels are becoming commodity items, and inverter technology is moving to commodity rapidly. Consequently, construction costs and other labor driven costs are becoming dominant and efforts should be taken to decrease time and costs associated with construction and maintenance phases of future projects.
- The process by which stakeholders could review real-time energy production could be clearer.
Due to adverse market conditions, Nanosolar ceased their manufacturing operations in October 2013. Unfortunately, similar to other American solar panel manufacturers, Nanosolar was unable to avoid effects from declines in solar prices caused by other countries flooding the American market with large quantities of low cost solar panels. However, the price decline of solar components used in the design and construction of solar plants means solar energy production can achieve grid-parity in many markets. This is particularly true in markets with high solar irradiance and daytime peak-time rate structures.