Point-of-Use PV Factory

Written by Peter DiSessa | 24 February 2013

The solar PV utility market is experiencing significant growth that will continue through the foreseeable future. In the US alone, utility companies are expected to add at least 20GW of solar PV to their power generation portfolios by 2020. This rapid growth in market demand is driving development of utility-scale solar PV power systems such as grid-tied solar farms of 20MW to 200MW. These farms will consist primarily of crystalline silicon (c-Si) modules, due to utility demands for reliability, high efficiency, a proven “bankable” track record with a demonstrated 25-year life span, as well as overall module and balance of system (BOS) capital cost considerations. PV power system capital investment remains a major consideration in these growth projections, and further PV power system capital cost reductions will be necessary to drive accelerated growth of utility-scale solar PV over the next decade.

New highly automated PV module manufacturing equipment and process technology are being developed for the production of “supersized” 1kW utility-scale solar PV modules.

New highly automated PV module manufacturing equipment and process technology are being developed for the production of “supersized” 1kW utility-scale solar PV modules (Figure 1). Such larger modules provide significant PV power system capital investment reduction by helping to reduce module and balance of system (BOS) expenses, including installation costs. A single, larger 1kW PV module will provide cost advantages compared to smaller conventional size modules. The “supersized” 1kW module essentially transfers a significant amount of a PV power system’s costs from field installation to the PV module factory where 1kW modules can be mass produced at lower cost.

These advantages yield a total estimated PV power system cost savings approach a range of $0.10/W - $0.15/W (Figure 2). For example, a $0.11/W PV system cost reduction is equivalent to a capital cost savings of $11 million dollars for a 100MW utility-scale farm and an energy savings of $5.00/MWh.  This cost reduction would translate into hundreds of millions of dollars in savings over the next decade for this rapidly growing market segment.

Figure 2 – PV Power System Cost Comparisons per Watt

Rationale for “Supersized” 1kW PV modules

The output for a conventional PV module is a range of 240W-300W depending on cell and module efficiency.  Larger modules, up to 400W, have been recently introduced and are targeted specifically at the PV utility market. “Supersized” 1kW modules, more than double this size, could provide even greater benefit for PV utilities. However, very large modules are impractical if they require transportation over significant distances. The transportation complexities for the “supersized” 1kW module provide an incentive for local PV module manufacturing at the point-of -use of the solar farm site or at a centralized location with multiple customers nearby. The modest expenses associated with building a local module factory would be quickly offset by savings realized from the larger 1kW module design. More importantly, the transportation constraint does not apply to the key materials that go into a module; i.e., the solar cells, which are small and light, can be tightly packed.

An important consideration is how to address a factory designed to service a limited, exclusively local customer base. The solution is that the PV manufacturing equipment and 1kW module factory can be easily moved every few years. At the completion of each solar farm project, the factory can be decommissioned and the equipment relocated to another solar farm site to continue manufacturing 1kW modules.

Cost and performance benefits are summarized here:

• Reduced installation cost

1. o   More power per panel means fewer panels in an array
2. o   Easy installation and lower cable cost
3. o   Reduced labor cost results from fewer module interconnects
4. o   Quicker installation period compared to conventionally sized modules

• Reliable and robust design

1. o   Design to the highest industry standards
2. o   Bankable and reliable  c-Si solar cells, low iron ARC tempered front glass, sturdy reinforced frame with high mechanical load capability

• More power per unit area

1. o   More power produced in the same unit area with c-Si cells at high efficiency and lower frame “parasitic” area
2. o   Lower transmission losses – higher energy yield

• Less space is required

1. o   Superior land coverage ratios

A design is available for the 1kW “supersized” module, which will be nominally 5.5-ft × 12.5-ft (1.6m × 3.8m) and made with (240) 156mm multi-crystalline silicon solar cells connected in 10-cell strings. Using cells with a nominal output of 4.19W/cell (with 17.2% cell efficiency) will produce a nominal module power of 1kW; module efficiency with low ARC glass is estimated to be 16.1% (Figure 3).

Figure 3 – 1 kW “Supersized” Module Specifications

Figure 4 – Standard PV Panel composed of four 250W modules (top) vs. 1kW module (bottom)

Figure 4 above illustrates several BOS cost reduction areas. Current estimates indicate savings of $0.10-$0.15/W can be achieved through the installation of PV systems nearing 20MW.  Specific BOS savings can be attributed to decreased packaging and shipping costs, a significant reduction in required racking materials, decreased quantity of ground lugs and wire management, and a reduction of power inverter/converter units.

Figure 5 below shows potential BOS savings compared to a conventional installation.

Figure 5 – “Supersized” kW Module Balance of System Savings

Some BOS costs, such as land, foundation, and permitting cost, are not included in Figure 5. However, these costs are the same for both module types, so the cost savings are not affected.

Module assembly process seeks LCOE

The method described here is a way of leveraging innovation in module assembly process technology to achieve a lower levelized cost of electricity (LCOE) for PV power systems. The specific product innovation is the development of the 1kW “supersized” module that has an equivalent module production cost compared to conventional 250W modules. However, once the differences in BOS installation costs are factored in, there is a clear advantage of approximately $0.10W-$0.15/W for utility-scale solar farms approaching 20MW.  For example, a $0.11/W PV system cost reduction is equivalent to a capital cost savings of $11 million dollars for a 100MW PV power system and an energy savings of $5.00/MWh. For a 100MW PV power system located in a region that produces Southwest US amounts of sunlight per day, the accumulated energy savings has a value of over $15 million dollars during a 20 year lifetime. The point-of-use factory for 1kW “supersized” modules is arguably one of the most effective ways to shrink the LCOE to attain grid parity with fossil fuel-produced electricity.

Written by Peter DiSessa, Vice President of Worldwide Sales at Spire Corporation based in Bedford, Massachusetts (US).