Wednesday 4 September 2019

Solar Thermal Innovators

Are These Solar Thermal Entrepreneurs Going to Move the Dial for Solar Thermal?

At the "Setting Sights on Scottish Solar 2019" conference this week in Edinburgh,  we heard from three individuals that are hoping that their innovative ideas are going to set the solar thermal market alight again.

Since the glory days of 2010 when, according to statistics from the Solar Trade Association, the UK installed nearly 90,000 square metres of solar thermal panels the market has reduced in size every single year.  Only 7,000 square metres were installed in 2018.   In an introduction to the session, the Chair of the STA's Solar Heating Working group, Dr Richard Hall revealed that this is not simply a UK phenomenon - solar thermal is in retreat in almost all international markets.

Annual solar thermal sales in the UK according to statistics compiled by STA

Solar PV panels continue to decrease in cost and increase in power output.  Excess PV-generated electricity can be inexpensively diverted to heat hot water in your tank via its immersion heater but can also charge large batteries to provide evening electricity use, and prevent a trip to the petrol filling station by topping up your electric car.  Where is the place for solar thermal in this brave new world of smart electricity grids and electricity 'pro-sumers'?
Our three brave entrepreneurs each believe that they have found a new angle that can make a difference to the appeal of solar thermal panels.

Image: SolarisKit

Faisal Ghani of Solariskit  sidesteps the problem of declining traditional markets for solar thermal by attempting to create a completely new market for solar water heating in sub-saharan Africa and other hot countries.  His 'flat-pack' solar panel features a black slinky hose arranged in a conic spiral and contained within a clear plastic pyramidal cover.   It is intended to be low-cost and simple to install and maintain.

solarblogger says: Faisal has come up with a really striking geometry for a solar collector and it is clear that the material costs could be low, if SolarisKit can get enough volume in manufacture.  It's low-weight, flat-pack design will doubtless be helpful for supply chains across rough terrain.  However it will be up against the most cost-effective of solar thermal panels - the thermosyphon Chinese combi systems that include a panel and an outdoor cylinder at rock-bottom prices.

Image: Soltropy

By contrast, Stuart Speake from Soltropy thinks that dairy farmers with a large hot water demand are ideal customers for his solar panel, and his business appears to be the furthest along of the three in that is financed by product sales rather than investors and grant money.  Soltropy's evacuated tube solar collector is freeze tolerant.  Water heated by the evacuated tubes as it is pumped along a copper header pipe returns down a second pipe made from a flexible, compressible material that runs inside the first.  If the water in the pipe freezes, the inner compressible tube is squashed up to prevent the pressure build up that would normally cause pipes to burst in freezing weather.  A solar thermal system that does not require antifreeze has greatly reduced maintenance requirements.

solarblogger says:  I love this idea- it achieves the same goals as the old Solartwin freezable absorber, but elegantly avoids that product's serious performance compromises by removing the compliant tube from the heat transfer pathway.  There is no doubt that the breakdown of antifreeze over time is the source of many of the reliability issues of solar thermal, and that many customers simply don't do preventative maintenance on their solar heating systems.  Being able to reliably remove antifreeze from solar thermal is a big step forward, but I'm not sure that on it's own it is enough to change the fundamental attractiveness of the technology.

Image: Senergy

We also heard from Christine Boyle of Senergy, whose company has developed an all-polymer solar thermal panel.  The absorber, fluid flow channels and panel sides are extruded from specially developed material consisting of  carbon nanotube loaded polymer.  This new material has high softening temperature compared to most other plastics, improved thermal conductivity and increased strength. The latter of these properties of the material allows it to be made with thinner walls which also enhances heat transfer to the working fluid.

The extrusion is finished off with injection moulded end-caps to complete the fluid circuit and a clear polycarbonate coverglass is added on top.  There are inevitably some performance penalties compared to conventional solar collectors, the insulation is de-rated to limit the stagnation temperature and the absorber is not spectrally selective.  The energy yield will be reduced to some extent for most applications, but  Senergy claim that their panels are 50% of the price of regular solar thermal panels, which if it is borne out would represent a very significant saving.

solarblogger says: All-polymer panels have been seen as the holy grail of low-cost solar thermal by many people for some time.  Other advocates include Aventa Solar from Norway, which has developed an all-polymer absorber, but I really like the design for manufacture that Senergy has come up with.  However, I remain pretty sceptical that a lower panel cost will be a silver bullet for solar thermal.  Conventional solar thermal panels  made in vast quantities, for example by GreenOneTec  leave the factory for less than EURO 100/m2.  Consequently the manufactured cost of the panels represents less than 10% of the price of a typical domestic-scale installation, with other costs such as customer acquisition, roof access, piping, insulation and controller accounting for the rest.

So what do you think, are these three solar thermal innovators going to be the next big thing or are they trying to push water uphill in such adverse market conditions for solar thermal?