Days after getting an administrative reprieve for a massive solar project, things aren't looking so hot for Stirling Energy Systems and its development partner, Tessera Solar.

Steve Cowman, who was the CEO at SES until recently, has left the company, as have a number of other executives. Meanwhile, Tessera laid off between 50% to 80% of its employees last month, according to sources. Rumors began percolating about problems at the companies, which work together and are part of an Irish conglomerate called NTR, last month. Sources close to the company have now confirmed Cowman's departure and the layoffs, but not the number of layoffs.

Tessera and SES want to build massive solar thermal parks in the Southwest based around the SunCatcher, a mirrored dish that directs hot air toward a Stirling engine to produce power. An individual SunCatcher can generate up to 25 kilowatts of power. In October, the Department of the Interior approved two projects proposed by SES and Tessera: the 709-megawatt Imperial Valley project and the 663-megawatt Calico project. California regulators approved Calico (after first rejecting it) on December 1.

Unfortunately, the companies also need money. Brett Prior at GTM Research estimated in October that the companies would need to raise $200 million in equity and $160 million in debt  and qualify for federal conditional loan guarantees before the end of the year in order to qualify for U.S. Treasury grants that will cover a substantial part of the construction on Calico alone. The deadline for the grants is the end of the year and the equity, debt and loans will be needed to start construction or buy equipment for it, necessary preludes to the Treasury grants. In all, Calico might cost $2 billion or more.

The layoffs and executive departures (Cowman was not the founding CEO, by the way: he got the job in 2008) could be a hint that the fundraising process is not going as planned.

“We don’t discuss individual staff-related actions. I can confirm, however, that as we transition out of the active development stage now that the California projects have been approved, we’ve recently restructured the businesses to manage expenditures,” said an official spokesperson for Tessera.

The bright side could be the projects themselves. Conceivably, SES and Tessera could sell their projects to other solar developers with different solar technologies and money in hand if SES and Tessera can't get loans and funding. Stay tuned.

Rival Brightsource Energy, which relies on a very different technology known as power tower, received administrative approvals around the same time, but it also has received a conditional loan guarantee on its Ivanpah project and started work. NRG Energy also agreed recently to invest $300 million into Ivanpah.

Beyond the usual headaches surrounding raising millions of dollars in a short period of time, SES and Tessera face perhaps an even bigger hurdle. Solar thermal plants aren't as attractive as they were in 2007. Back then, solar thermal was the technology of choice for big solar parks. Declining prices of silicon and silicon solar panels, however, have caused developers and utilities to switch over to building these with PV panels.

In 2010, the price to build a solar thermal park run by troughs, power towers or dish engines runs between $5.00 and $6.55 per watt. On the other hand, utility-scale PV projects can squeak through at less than $3.50 per watt, as we noted in an article in October. One of the big symbols of this shift came when First Solar, the big PV maker, took over a project from thermal specialist Ausra in 2009 and turned it into a PV project.

By 2020, the thermal solutions are expected to be in the $2.40 to $3.80 per watt range, but by that time, PV plants could be below $2 a watt.  Trough and tower plants could conceivably catch up and beat PV in price on large-scale projects, but it would be tough.

Solar PV parks are also modular: developers can build 10 megawatt parks, or scale them up to 250 megawatts. Solar thermal parks are larger, and thus come with more logistical headaches.

To top it off, unlike troughs or power towers, Stirling engines do not have inherent capabilities for storing heat to make power after the sun goes down. (The other technologies transfer heat via liquids; Stirlings use air hydrogen.) While some utilities are opting not to put storage capabilities into their solar thermal parks at the moment, it remains one of the more attractive features of solar thermal. Stirling engines also have more fast-moving parts, which can break down more readily.