Many perspectives on solar generation undervalue or devalue the technology because utilities can’t depend on it to provide steady, predictable amounts of power as they can on traditional fossil-fueled or (dare I mention) nuclear-powered generators. The thought process is solar-generation facilities produce only during daylight hours and, under best conditions, they lie dormant for half of every day.

PAR for the course
This perspective ignores several conditions under which grid power generation and distribution resources operate: Grid utilization is highly time-of-day dependent, exhibiting large and mostly growing peak to average ratios (PARs) with peaks tending to occur during afternoon hours.

For example, in 1993, New England peak power demand exceeded the average by 52 percent (table 1). By 2012, the most recent year for which data is available, that figure had grown to 78 percent, down from the previous year’s topper of 89 percent.

Figure 1:	Average cost of US residential electric power and year-to-year price growth rate.( Credit: Energy Information Administration, US Department of Energy)

In Southern California, the 20-year worst-case PAR was 1.96 in 2010, meaning that electric power generation and distribution capacities had to accommodate roughly twice their average load even before padding for safety, reserve capacity, load power factor, and growth.

Grid and bear it
Market conditions have changed — in some cases dramatically — altering the economic context in which we judge solar technologies. Currently, generating plants are facing significant challenges. For example, in September this year, the US Energy Information Administration (USEIA) reported that electric-power-sector coal inventories had fallen 22 percent from last year, reaching eight-year lows. Of the 4.1 PWh of electric energy generated in the US during 2013, 39 percent was fueled by coal.

In the south, where electric-power generation relies heavily on coal, inventories are down 29 percent. Utilities in the midwest, another region highly dependent on coal-fired power generators, also report issues with low coal inventories after coal-car loadings recently fell for eight out of nine weeks. One Wisconsin utility reports it may have to limit or cease operations while a generator in Minnesota has already reduced output power to conserve fuel.

Natural-gas-fired power generation facilities, responsible for 27 percent of the US total, are also under pressure with double-digit percent price increases in the most recent year: July to July prices to electric utilities have increased 23.7 percent between 2013 and 2014, according to US Department of Energy (DOE) data. The price increase to independent power producers over the same interval is even greater at 30.8 percent.

The aggregate stress in US electric power-generating operations reflect in power pricing, set to spike in some regions between now and the end of the year. For example, UK-based National Grid — one of New England’s top electric-power providers — has announced residential electricity rates will increase 37 percent year over year, starting in November. Nationally, year-to-year residential rate increases have averaged 3.2 percent per year for 13 years, according to USEIA data (figure 1), but industry sources reference this year’s increases in natural gas prices as well as reduction in nuclear and coal-fired generation capacity in the region. Another major provider of power to the New England region, NStar, has also issued warnings of higher rates, though they remain coy about the numbers.

Exacerbating the regional market conditions, the 620 MW Vermont Yankee reactor will cease operation by the end of this year. According to DOE data, the average age of commercial nuclear-powered electric generation facilities is 33 years, so we can expect notable capacity reductions in other regions in the coming years.

Table 1:	US grid power: average, peak, and PAR data, 1993 through 2012)

Solar rising
Solar installations will not make up for electric power generation capacity stresses in the immediate term, though installers I’ve spoken with report healthy upticks in new orders. With fossil-fuel inventory availability, generation capacity, and price volatility continuing to affect non-renewable generation negatively, distributed generation, and solar in particular, are increasingly attractive for several reasons.

As installed capacity ramps up, solar generation will help mitigate peak demand and reduce generation PARs. Because it provides distributed generation, small-scale solar serves the same purpose for distribution grids and can reflect that benefit back onto transmission networks when solar adoption rates reach sufficient levels.

While fossil-fuel prices are soaring and availability is growing less reliable, solar energy fuel costs are highly predictable, free. Enormous quantities of the non-polluting solar fuel arrives fresh daily with no transportation costs or logistical complexities.

With few exceptions, such as in architecturally historic districts and the entire state of Florida, residential and small-scale commercial solar installations face low bureaucratic impedances to siting and permitting. Low system costs and short installation sequences minimize financial risk. Systems readily scale from single-family residences to office parks, allowing the industry to take advantage of economies of scale for key components.

Although the most advanced photo voltaic (PV) cell technologies reach commercialization slowly, parallel improvements to manufacturing-process methods have been effective in reducing panel costs and increasing efficiencies (figure 2). For example, poly-Si PV-wafer manufacturer’s costs have fallen to about $0.20/W — roughly one third of what they were six years ago.

Recently, Michigan State University researchers developed a transparent luminescent solar concentrator (TLSC), which absorbs certain wavelengths of light. According to Richard Lunt, an assistant professor, a TLSC can “pick up just the ultraviolet and the near infrared wavelengths that then glow at another wavelength in the infrared.” The TLSC guides the glowing infrared energy to the edge of the material, where narrow strip-shaped PV-cells convert the energy into electricity.

An important attribute of the TLSC is that it is transparent in the visible spectrum without color artifacts. This allows manufacturers to laminate TLSCs to windows, cell-phone screens or any other clear material. Lunt reports, “It can be used on tall buildings with lots of windows or any kind of mobile device that demands high aesthetic quality like a phone or e-reader.” When commercialized, the TLSC can greatly increase the surface area available to residential and commercial building owners for solar power generation and do so with no visual clutter.