Canada's Sun Simba vies to be next king of the CPV jungle

Innovative module promises to make solar energy cheaper than coal and natural gas.

Completion of a $25m round of fundraising at Canadian concentrating PV (CPV) outfit Morgan Solar late last year is oiling the wheels for the roll-out of its innovative Sun Simba module, with a string of commercial-scale deliveries slated for the first half of 2012.

Sun Simba is an integrated “non-cell” PV concept built around a patented light-guide solar optic (LSO) structure — an ultra-thin acrylic and glass arrangement designed to “trap and transport” sunlight on to a triple-junction III-V cell fitted at the centre of the module.

Unlike conventional lens-based CPV systems, the LSO is sealed to the cell, eliminating thermal-expansion issues and cutting out the bulkiness and related material costs common to many concentrator systems.

Early performance tests of “unoptimised” Sun Simba prototype modules, which are calculated to concentrate sunlight by the strength of more than 1,000 suns, returned efficiency rates of 19.5%, with expectations that 35% is within reach for the latest version of the technology.

“When we get the Sun Simba commercialised on a scale compatible with some of the largest module makers in the world today, it is going to be grid-competitive with every other source of energy — we will be cheaper than coal and cheaper than [natural] gas,” states Morgan Solar president John Paul Morgan. “And it will help any and all who want to produce power at lower cost, whether based on distributed or centralised generation, rooftop, whatever. This technology is going to provide economics that are going to match or better the best economics of traditional fuel sources.”

The chief innovation of the Sun Simba module, now into its third-generation design, is the LSO, which functions like a Fresnel lens with a “zero-degree” focal length. When sunlight strikes the surface of the panel, it is drawn through the material radially along polymer optic micro-channels called “light guides” to the PV cell at the centre.

“With a zero-degree focal length you can build high-concentration flat panels that are inexpensive, light and do not need breathing apparatus because there is no air space in the panel,” says Morgan, an optical scientist.

The LSO also blocks infrared radiation from reaching the PV cell — the small loss of power being compensated for by the cooler cell’s higher efficiency.

“When I started to design [the LSO concept] I looked at all the lens-based systems and they all looked like they had been designed by a mechanical engineer [trying] to solve the myriad problems involved in keeping a lens at the proper focal length from a cell with a 0.1­millimetre locational accuracy over a 20-year lifetime. To say nothing of the challenges of creating air cavities [between lens and cell] that require a kind of breathing apparatus to keep them from overpressurising and so on. Then moisture can get in, so you have to add dessicant [a drying substance] and so on.”

Material costs are at the nub of it. Concentrate light into a cell “as a whole panel” and there is a “vast difference” in the capital expenditure needed to build a PV farm “several football fields in size”. “To make an impact on global energy prices you need to use as little material per watt as possible,” Morgan adds.

Back-of-the-envelope “total internal reflection” calculations, based on “etendue” optics theory, which deals with how light spreads out by area and angle, led to the first sketches of the LSO for the Sun Simba module.

The choice of PV cell, made up of stacked layers of gallium indium phosphide, gallium arsenide and germanium — as has long been deployed on space satellites — was a matter of “using the state of the art in terms of efficiency”, says Morgan, although the LSO technology is cell-agnostic.

Driven by expected refinements to PV cell technology, Morgan Solar’s “efficiency road map” puts the 35%-efficient module milestone “just a few years away” and 40% on the horizon.

The Sun Simba’s novel frame and tracking system have been fashioned in-house. A dual-axis type, the concept is based around a lightweight “self­ballasting” structure that eliminates concrete foundations, and the incumbent heavy-lift cranes or civil works machinery, from the development equation. It is wired in to the modules before they are shipped to site for installation.

A Sun Simba array is designed to operate in winds up to 50km per hour (km/h), swinging into “stow” position if the gusts hit 110km/h, and able to survive storms of 190km/h.

Morgan Solar estimates the levelised cost of energy for an industrial-scale development of Sun Simbas, which are expected to be 99% recyclable, would ultimately come in at less than $0.05 per kWh.

The promised economics of the technology have won over a wide range of investors. In its first tranche of funding — the company has managed to raise $38m so far — stakes were taken by Spanish energy group Iberdrola, US precision injection moulding outfit Nypro and private-investment firm Frost Group. Canadian oil and gas company Enbridge is the latest to invest, stumping up almost $10m last November.

A factory in San Diego owned by Nypro is preparing to ratchet up module production capacity from 16MW a year to about 50MW by the end of 2012.

“We are not looking to build capacity on spec. This ramp-up will be in response to expected market pull,” notes Morgan.

The company has three demonstration sites in operation in Canada, and a fourth in the US’s Mojave Desert. The first prototype installations of fully integrated Sun Simba modules mounted in Toronto and at the University of Ottawa have been “under the sun” since early 2009, being put through their paces to gauge durability and efficiency.

“These units have been kicked about quite a lot,” says Morgan, “and they have come up well — a solid piece of work, no degradation to speak of. They started producing at 19.5% efficiency and have been flat-line at that level for quite some time now.

“We found these second-­generation units, while they were high­efficiency, were difficult to mass produce and still be high­efficiency.

“The technology wasn’t at issue but these tests allowed us to learn which manufacturing processes worked well and which didn’t. The good news has been that we have been able to take this knowledge and work with Nypro to iron out these pro­cesses and get our third­generation modules built in such a way where we are getting very high output unit to unit now.”

A 5kW third-generation Sun Simba prototype has been deployed at Morgan Solar’s test location in the Mojave, with another 145kW of modules brought on line late last year at a third-party site nearby. Further 100kW demonstrators in the region are being developed, “backed by customer commitments”, for imminent switch-on.

Plans are also afoot to set up at test site “relatively soon” in India.

“A lot of people in the CPV sector say that anything under 7kWh per square metre per day of DNI [direct normal irradiance] is not economically touchable but that is down to the cost of their systems,” stresses Morgan.

“Get into an inexpensive system like ours and many of the otherwise marginal areas [for solar-power production] open up, which is important because most of the world is not under sunny blue skies X-number of days of the year.”

Thin-film economics are the benchmark against which Morgan Solar is judging its chances. According to Morgan, a $0.90/W manufacturing price per panel is “definitely within reach” at start-up of the San Diego assembly line, dropping down the cost curve to be below $0.40 “within three to five years”.

“The fundamental reason for progressing CPV is that if you look at solar-power technologies around the world, there are only a few that are truly scaleable to the multi-gigawatt level,” argues Morgan.

“The material supply chains required to build cadmium-telluride thin-film at this scale, for instance, are self-limiting. Whether it is 20GW or 100GW, I think there is going to be a point reached where there is a price correction. As certain types of modules climb up in volume on the supply chain side, that is really going to inhibit their ability to reach truly competitive pricing at a scale that is meaningful in terms of making a dent in the existing power-production paradigms.”

CPV, he says, is one of the few that “uses commodities that can be scaled to match demand for thousands of gigawatts” and the only one “with a great deal of innovation still ahead of it”.

“I am interested in power and making it cheaper to produce, because power equates to quality of life. For me, my money is on CPV.”

Lightweight system keeps its cool

The LSO (light-guide solar optics) structure developed for Sun Simba led from the front as the new module was developed, but the later-designed Savanna tracking system will play a key supporting role in the economics of the technology.

The 720-watt (W) LSO panels, which measure three square metres, are fixed in fours onto a rectangular steel frame that is fitted with dual-axis trackers on each corner. The panels are spaced vertically in a “staggered row” arrangement, allowing cooling by convection, with hot air escaping up and through the structure. Even in extreme environmental conditions — 50°C, 850W per square metre of direct sunlight, zero wind and no humidity — the modules are anticipated to be “well within” operating limits.

“We’ve gone with the ‘small and many’ rather than ‘few and big’ approach because we feel that there are benefits in cost and economies of scale for fabrication,” says Morgan Solar president John Paul Morgan. “And we are able to build two-axis tracking systems that are extremely reliable using gearboxes with millions of hours of testing under their belt.”

Staggering the placement of the modules also lightens wind loads by some 30%, meaning less beefy tracking systems can be used.

In line with a cost-cutting philosophy, Morgan Solar devised a proprietary lightweight, “human-scale” tracker for the Sun Simba modules that removes the need for concrete foundations, heavy-lift cranes or civil works machinery during installation, to bring down the balance of system, installation and development expenditure.

The Savanna tracking system uses a “self-ballasted” design, which makes it possible for pre-wired arrays to be shipped in packing crates, transported to site almost irrespective of road infrastructure, unfolded and deployed rapidly “by a team of unskilled workers with simple hand tools” on most terrains.

This approach was driven by chief executive Asif Ansari, who joined the Toronto-based company from Los Angeles giant eSolar, based on his experience of building a solar-thermal development in India.