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?

Solar Thermal in the Crosshairs

Bullet Point Needed for DECC Action Plan

The Department of Energy and Climate Change (DECC) has released its consultation on reforms to the Renewable Heat Incentive (RHI), and this time it looks like it’s the turn of solar thermal to be under threat.  DECC's intention is to completely remove support for solar thermal by dropping it from the RHI while support for other renewable heat technologies such as heat pumps and wood chip boilers continues under the scheme.

As the solarblogger shows below, it's relatively straightforward to pick holes in the government's arguments for singling out solar thermal.  Whether DECC will be swayed from what is looking more and more like an ideological attack on solar is more open to question.

Busting The Arguments

DECC says:
Solar Thermal technologies account for 17% of total accreditations (7,445 out of a total of 45,111) but just 2% of heat (11TWh out of 598TWh).

Solarblogger says:
Solar thermal delivered 2% of all heat (11TWWh out of 598TWh), but accounts for only 1.4% of committed budget at the end of 2015 (£0.69m out of £49.3m).

So what?  So what if each solar thermal system contributes a small amount of energy?  It’s being unfairly compared to massive biomass boilers heating country piles, factories, and barns!  We already knew that solar thermal was more likely to be applied to domestic hot water in normal family homes where the small amount of energy each installation delivers still represents a significant proportion of household energy consumption (around 10%).

If affordability is the basis on which solar thermal is to be excluded from the RHI, then surely the relevant statistic isn’t to compare the proportion of all installations against the proportion of total heat, it’s to compare the cost against the heat delivered.  On this basis solar thermal looks much better value for money.


UPDATE (4.4.16) - figures should be treated with caution.  The committed budget is forward-looking and the delivered heat is backwards-looking, so it seems likely that large numbers of biomass boilers installed in the current year will be increasing committed budget but not contributing greatly to historic delivered heat.  Research into OFGEM figures by Mike Landy at the STA suggest that solar thermal represents 2.8% of payments made under RHI for 2% of delivered heat.



DECC says:
When asked, around half of all owner-occupier applicants said they would have installed it anyway.

Solarblogger says:
The DECC survey asked people to report their motivations for doing something after the event.  Such surveys are prone to a well-documented error called social desirability bias.  This is a tendency of respondents to answer questions in a way that paints them in a good light.

What DECC fails to mention is that the proportion of owner-occupier applicants saying that they would have installed other RHI technologies anyway was also extremely high.

Proportion of respondents saying they would have installed the same technology irrespective of the availability of the RHI:

Biomass         11%
ASHP 31%
GSHP 32%
Solar Thermal 49%

Installing renewable energy systems is seen as doing a social good.  People are less likely to admit that they only did it because of a government bribe.  The less expensive the system they have installed, the more ‘embarassing’ it would be to admit you wouldn’t have done it without the RHI.

The survey is flawed and to rely on it as a reason to take such a significant action against solar thermal is shocking.

DECC says:
We judge solar thermal to be a mature technology with a well-established global supply chain.  It is not clear that ongoing RHI support will serve to build this supply chain in the way that it can for other less mature technologies in the UK like heat pumps.

Solarblogger says:
Again solar thermal is being unfairly singled out.  A well-developed global supply chain for solar thermal is being compared with an immature domestic (UK) supply chain for heat pumps.

Heat pumps also have a well-established global supply chain, due to their high deployment in other European countries (27 million in operation across EU) according to Eurobserver and 1.7million heat pumps were sold in the EU in 2014.

Just like for heat pumps, solar thermal has a strong global supply chain but a nascent UK supply chain.  Just like for heat pumps, action to stimulate a strong UK supply chain has the prospect of reducing costs in the UK.  The Solar Trade Association estimates by as much as a 30% reduction in costs for a volume UK market of 200,000 systems a year.

Past Performance is not an Indicator of Future Success

DECC argues that deployment rates for solar thermal are too low to justify keeping solar thermal in the RHI, and that they can’t increase the subsidy levels as they are already set at the so-called ‘Value for money’ cap agreed with Treasury.

If the folks from DECC had been able to find an unconflicted solar thermal company to talk to (one that didn’t also make a living from PV), and asked them what was the one thing it could do to grow the market for solar thermal, the answer would have been “Reduce the subsidy for PV”.

The Feed in Tariff had four years’ head-start on the domestic RHI and domestic solar PV launched with tariff levels four times higher than the cap imposed on solar thermal.  Until the most recent shock reduction in the Feed in Tariff, support for PV was still higher than the cap (taking into account that the domestic RHI is for seven years, and the FIT is for 20).

Add in the loophole that pays owners of solar PV systems for exported electricity, even when they divert that power to heat water instead of exporting it and it’s obvious that the real reason for solar thermal underperformance is more linked to decisions made in the department at DECC that looks after the Feed in Tariff.

The Feed in Tariff has now been cut to a level that gives a much more level playing field with solar thermal, and many installers were starting to re-boot their solar thermal expertise and explore this option.  A recent survey of member companies by the Solar Trade Association found level of enquiry for solar thermal running at double the rate of the previous year.

The tragic mistake that the Heat team at DECC might be about to make is to have reached their conclusions about the performance of solar thermal based on a period during which a separate department at DECC was supporting PV much more generously.

Fixes Needed in RHI

Linking the domestic RHI to the Green Deal was a mistake, and the cost of having to get a Green Deal Assessment affected solar thermal disproportionately compared to more expensive technologies.  The decision to remove this requirement would boost solar thermal.

Solar thermal is an excellent companion to heat pumps, taking the strain on high temperature domestic hot water and allowing the heat pump to focus on working at lower temperatures, where its performance is more optimal.  The domestic RHI tried to reward people that installed both technologies together by allowing them to claim support for domestic hot water for both heat pump and solar.  Unfortunately the regulations were drafted in a way that ruled out the most popular implementation of a combined heat pump/solar system – a thermal store, see my earlier blog on this cock up here.  The Solar Trade Association has proposed a number of different ways that DECC could have fixed this problem to boost solar thermal deployment, suggestions that were sadly, ignored.

The proposal to remove solar thermal from the RHI is based on flawed logic.  The market has changed drastically since funding for PV was cut and early signs since then show indications of a return to growth.  Domestic hot water is the heat load that cannot be insulated away and solar thermal has an important part to play in decarbonisation our homes and addressing fuel poverty.

DECC should continue to support solar thermal and fix problems with the RHI that are holding it back rather than throwing it out of the RHI.

Solar Attrition Rates

An Analysis of the MCS Installer List

I recently had the opportunity to have a look in more detail at the list of installers registered with MCS, and what I found came as quite a surprise to me.

The number of solar PV installers registered with the Microgeneration Certification Scheme (MCS) has been on a declining path since the boom of 2010-11.  This is not news to anyone in the industry.

Right now, the number of solar PV installers registered with MCS (removing duplicates) is around 2,640, a fall of 24% since 2013.  But when you look at the actual companies that make up this headline figure you find that less than 50% of the solar PV installation companies on the list in 2013 remain two years later. 1,822 companies have left the market, but 980 new companies have joined the list in the last two years.

Churn Rates in Solar Installation Businesses

Turning to the list of solar thermal companies, we see that the decline in numbers has not been as severe as for the PV installer companies, a 13% drop from 1,298 companies in 2013 to 1,130 now.  However, the churn rate is just as eye-watering.  Nearly half of the solar thermal installers registered with MCS in 2013 are no longer on the list, but the 635 that have left have been replaced by 467 new companies.

What's going on?  Are these attrition rates normal for similar industries (home improvements, heating, electrical works)?  Or is there something 'special' about our solar industry?

The Impact of Solar PV and Solar Thermal on EPC Ratings

The EPC Rating is a score between 1 and 100

Introduction

The Energy Performance Certificate (EPC) is a fundamental plank of the government’s strategy to improve the energy performance of the UK’s building stock.

• Since 2007 it has been a legal requirement that homes for sale have a report of their energy performance for potential buyers.
• From 2018 it will be a requirement that rental properties have a rating higher than E.
• In Scotland, all social housing will have to achieve an energy rating of C or D (depending on house type) from 2020
• To access the Feed in Tariff for solar PV, it is necessary that the building achieves an EPC D rating
• To access the domestic Renewable Heat Incentive, it is necessary to undergo a Green Deal Assessment, which is essentially an EPC with added extras to factor in the way you use energy.

The certificate rates buildings with a score from 1 (least efficient) to 100 (most efficient), with the scores divided into bands A through G as shown.

How it is Worked Out?

An approved calculation called the Standard Assessment Procedure (SAP) is used to calculate the energy used to heat the home, provide hot water to occupants together with electricity for lighting, pumps and fans.  Electricity used by other appliances is not considered.

The actual number of people in the house and the way it is heated is ignored.  A standard occupancy and a fixed indoor temperature is assumed – the idea is to compare the building with other buildings, not compare one set of occupants with another.

The energy used (gas, electricity oil) is then multiplied by fuel cost factors to produce a calculated energy cost for the property.  The energy cost is normalised by the floor area of the property to give a score between 1 and 100, the higher the score, the lower the building costs to run (with a house with a score of 100 nominally costing nothing)

For new homes the current calculation is SAP 2012 and the calculations are updated every time the building regulations change.

For existing homes, assessors use RdSAP 2009 (the Rd stands for Reduced Data).  This is an extra appendix to the SAP 2009 calculation which provides guidance on what assumptions to make when you don’t know or can’t see the exact specification of insulation and equipment.

Solar PV

SAP 2009 gives an unshaded, south-facing solar PV installation around 858kWh/year per kWp installed, irrespective of its the location in the UK.

Its calculation of energy costs assumes that 50% of the energy from a solar PV system is used in the dwelling and 50% exported (and this assumption does not change with the size of the PV installation).

The saving on the energy bills is then:

50% x energy generated x cost of purchased electricity

+

50% x energy generated x payment for exported electricity

In SAP 2009 the cost of purchased electricity is set to 11.46p/kWh for homes on a standard tariff, and the payment for exported electricity is also set at 11.46p/kWh.

Solar Thermal

A solar thermal installation could benefit the household energy bills in two ways.  First the solar system will generate heat that the boiler or electric immersion heater no longer needs to supply.  Second, a new solar hot water cylinder with better insulation will result in a reduced escape of heat from the stored water.  Although this heat loss contributes towards space heating in winter, but is wasted energy in summer.

SAP 2009 calculates out a solar energy input of 1,316 kWh per year for an unshaded 4 square metre flat plate installation, facing south and heating a 250 litre cylinder in an 85m2 house.  This translates into a fuel saving of 1,586kWh when the replaced heating system is a gas or oil boiler (taking into account their lower efficiency in summer months).

In addition the replacement of an old cylinder (where there is one) with a new would reduce heat losses.  For example, replacing a 50mm jacket insulated 180litre cylinder with a new 210 litre solar cylinder with 105 litre auxiliary heated volume and declared loss of 1.8kWh/day will save 444kWh/year based on a boiler winter efficiency of 90%.

Impact on EPC Rating

The impact on EPC rating of solar PV and solar thermal was calculated as follows.  For every SAP 2009 rating from 1 to 100, the implied Energy Cost Factor (ECF) was calculated by rearranging equations (10), (11) and (12) –  Section 12, page 33.  A house of 85 m2 floor area was considered, being the UK average size.

The energy cost that had resulted in that SAP rating could then be calculated from equation (357).

The saving on the energy cost was calculated by multiplying the energy savings from solar (discussed above) by the fuel prices in table 12.  The reduced energy cost was then converted back to a SAP rating.  The table shows the improvement in energy performance score for solar thermal and PV.

The impact of solar on a home's EPC energy score

NOTE: Figures shown are for a starting EPC score of 40 or higher (beginning of EPC band E), below this the size of the improvement decreases a little.

Conclusion

There are a growing number of drivers that are pushing building owners to improve the energy performance of their buildings.

Until recently, much of the focus has been on insulation measures to achieve these goals, but as more and more of the available cavity walls and lofts have been treated, the remaining insulation options such as external wall, internal wall and under-floor become disruptive and costly.

Solar thermal and solar PV are low hassle – high impact measures that can help increase the energy performance of homes.

Solar PV can give a significant boost to the energy rating of homes, particularly those with a clear roof of adequate size.

Solar thermal can be extremely cost-effective when combined with other heating system works such as boiler or hot water cylinder replacement and is more suitable for smaller roofs and partial shading.

Is This As Good as it Gets?

The Case for Good Looking Solar

Is that really the best you've got?

Do you like your coffee regular, large, super size or in a 6-litre bucket?  Americano, double espresso, flat, cappuccino?  Perhaps chocca-mocha or the icy one (whatever that’s called).  With skim milk, full fat or a drizzle of lard?  Do you want them to sprinkle brown dust onto the foamy topping for you?

Henry Ford famously said that you could have his Model T car “in any colour so long as it’s black”.  From the vantage point of our highly developed consumer market how amusing it is to imagine giving customers such limited choice.

Well, dear solar industry reader, why not take a fresh look at what are we offering our customers.

“You can have any solar installation so long as the panels are 2m x 1m modules fixed onto a rack above the roof, the array size matches a standard kit from a merchant and the panels are arranged in a nice easy rectangular shape.”

Yes, we talk about black-on-black modules or silver frames, poly or mono, micro inverters, optimisers or string inverters and all the rest, but are these technical issues really of interest to any but the earliest of early adopters?

Your home is your single biggest purchase and the roof is a very visible part of its kerb appeal.  If, when you come to sell it, a proportion of your potential buyers are put off by an insensitive solar installation on the roof it could cost you a lot of money.

Image: Viridian Solar Clearline PV30 and PV15 roof integrated solar panels

Forward thinking solar installation companies are already positioning themselves for a ‘post Henry Ford’ solar market.  They realise that as we move past early adopters chasing lucrative Feed in Tariffs and on to convincing the early majority to go solar we need to listen to people’s needs and offer them more choice, for example

• Downsizing the installation to avoid over-crowding the roof
• Grouping panels to create a more balanced, symmetrical installation
• Roof integrated systems where panels look more intended and less like an afterthought
• Large format modules for less clutter on the roof
• Solar tiles and slates
• Complete solar roofs
• Offering solar thermal for roofs with limited space

As the costs of the equipment for solar installations have fallen, the extra cost of roof integration has fallen to the point where it can no longer be ignored as an option for customers.


But  the industry needs to overcome some prejudices.

First, on ease of installation.

Removing a patch of tiles adds very little extra work.  This is especially true for large format concrete interlocking tiles, which are quickly lifted.  Integrated solar panels are not just for new build.

Second, on maintenance.

A PV system should last more than 20 or 30 years so the chance is high that some maintenance of a roof covering will be necessary.  Even new homes may suffer a single cracked tile from a manufacturing defect or mishandling during roofing.

Replacing a broken tile is a simple and easy job for a roofing contractor working from a roof ladder.  If the cracked tile is behind a solar array, then it’s a very different situation.  Scaffolding is required, an electrician is needed to disconnect the solar and then remove panels to hunt for the source of the leak below.  A simple job costing £100 has become a costly exercise that could comfortably exceed £1000.  Looked at this way, roof integrated systems are preferable.

Third, on energy performance.

Everyone knows that integrated systems are going to run hotter than systems that have more open to ventilation, but how big is the actual effect on energy yield?  Viridian Solar recently published research on this subject in collaboration with the University of Cambridge Department of Engineering.  The answer turns out to be only 3%.

A new, sophisticated and more demanding breed of customers is emerging for the solar industry.  Less interested in details of the technology and less accepting of “one-size-fits-all” solutions.

More and more solar installation companies are seeking to escape the race to the bottom by differentiating their offer.  Building integrated solar panels are a way to broaden the appeal of solar to more customers and add value to your business.


This article first appeared in Solar Business Focus UK Magazine

Is RHI More Trouble than it’s Worth?

To get support from the domestic Renewable Heat Incentive (RHI), there are some hoops it’s necessary to go through, but how much do these add to the cost of a solar thermal installation?

If you install a solar thermal system in the UK you can receive financial help from the government’s Domestic Renewable Heat Incentive (RHI).  RHI payments vary depending on factors such as the size of the solar panels, their location and orientation and especially the hot water demand of the house (which is taken from the number of people who live there).  It can be worth between £1,500 and £3,500, paid out over the first seven years.  In addition to the payments householders also benefit from savings on energy bills, the value of which are much higher the RHI payments over the long life of the solar heating system.

In order to qualify for the RHI, the solar panels must be of a certain quality - achieving accreditation with the Microgeneration Certification Scheme (MCS) or SolarKeymark, the installation company must also be MCS accredited and the household needs to demonstrate that it has taken straightforward energy efficiency measures such as insulating the loft and filling cavity walls (where there are cavity walls to fill).  The way that this last requirement is proven is to produce a Green Deal Advice Report that doesn’t show loft insulation or cavity wall insulation as a recommended measure.

In recent weeks it has come to light that some solar installation companies are advising customers that there’s so much cost and bureaucracy associated with installing a solar thermal system that qualifies for the domestic RHI that they are better off avoiding the scheme.

Let’s have a look at whether this argument stacks up.

Extra Costs for the Installation

Let’s assume that the installation is of identical quality both with and without the RHI.  The installer cuts no corners on the installation standard and that the equipment that is used is registered with the MCS or Solarkeymark.

The installer must log the installation onto the online MCS database for the customer to be able to claim the RHI. There is a charge from MCS of £15 to do this.  Let’s add £20 to that to pay for the time for someone to fill out the online forms.  Total £35

In addition, the household needs to pay a Green Deal Assessor to visit and produce the Green Deal report.  You don’t need to undertake any of the recommended measures unless they include loft insulation or cavity wall insulation.  The report costs between £150 and £250. 

So the total Variable Costs (cost per installation) are between £185 and £285

Annual Costs for the Installer

For an installer to be MCS accredited, there are annual fees to pay and administrative time required.  Let’s take a look at the costs for a smaller company, as it is generally thought that the burden is highest for these.

The solar installer must pay a fee to join the scheme and be audited each year.  For a solar installer with less than 10 employees the MCS annual registration and audit fee comes in at around £470 (see NAPIT fee sheet). 

In addition there is an MCS requirement that the solar installation company must be a member of an approved renewable energy consumer protection code.  Joining RECC depends on the number of staff, but for 1-6 employees it’s £250/year. 

Let’s assume the company wouldn’t operate a formal quality system if it wasn’t going to be MCS accredited and add £1,000 of admin time to these figures to pay an office administrator to maintain the paperwork that the scheme requires each year and make sure the document handover packs and quotes remain compliant with the scheme.

Both the fees and overhead costs fall (per technology) if the company installs other MCS renewable energy technologies as well as solar thermal, but let’s assume it doesn’t.

For this small company then, the total annual Fixed Costs of maintaining an MCS solar installer registration is £1,720.   

Total Cost

The total additional cost per installation of being RHI compliant is found by dividing the Fixed Cost by the number of installations the company does each year and adding this to the Variable Cost per installation.

This is where the costs of accreditation can start to look very high – it depends enormously on how many installations the installer does each year.  See the table below.

How the admin costs of an RHI compliant solar system varies with the number of installations
the installation company does each year

If the installer does only one or two solar installations a year then, yes the costs of RHI compliance is high compared to the benefit in claiming the RHI, but even at only one system a month the extra costs start to become really quite small compared to the RHI payments. 

The more installations that the company can do each year, the more the costs trends down towards the cost of the Green Deal Report.   Nor will every customer see this as a valueless piece of paper; some may value the guidance on further measures they could take to improve their energy efficiency.

The problem for the RHI is that until the scheme starts to drive demand for a reasonable number of installations, then for small companies that perhaps combine general plumbing with a very occasional solar installation the barrier costs of being MCS registered don’t look worthwhile. 

An excellent time to encourage a customer to consider solar heating is at the same time that a hot water cylinder is being replaced, but the plumbing company standing in front of the customer won’t offer this option if it isn’t MCS registered  If they do offer solar they might encourage the customer to ignore the RHI.  This is, of course, a classic chicken/egg situation.  Unless this plumbing company starts to offer more customers solar under the RHI, they’ll never see enough demand to justify MCS accreditation.

It would be good if there was a way to encourage this plumber to promote solar thermal to customers, perhaps in cooperation with a local accredited solar installer.  For any installation company that’s doing more than a handful of solar thermal installations each year, the cost of the RHI requirements are small relative to the RHI payments.

However this is not to say that MCS couldn’t do something to reduce the burden on smaller installers to meet the ever-increasing demands of the scheme.

Short of the Mark?

If you’re relying on a Solar Keymark wind resistance it turns out that there are large parts of the UK where you shouldn’t install

Viridian Solar has recently launched the latest version of its wind load calculator to partnered solar installers.  The calculator has been updated to take into account new guidance in the latest version of BRE digest DG 489 “Wind loads on roof –mounted photovoltaic and solar thermal systems”.

Read my blog on the changes to DG 489 here.

I thought I’d take the calculator for a test-drive, and decided to use it to try to answer the question “Is the Solar Keymark wind resistance test to 1,000 Pa adequate for the UK?”
The Keymark requires solar thermal panels to be tested for wind resistance, but historically it was a pass-fail test set at 1,000Pa (100 kg/ m²).    With the recent introduction of the new standard for solar thermal panels (ISO 9806), Keymark testing will require a pass-fail test at 2,400 Pa (putting it more in line with the level required for solar PV panels in EN61215).
 
However, the vast majority of solar panels currently on the Keymark and MCS database have been tested to the old standard EN12-975 at 1,000Pa.  While it is possible for the manufacturer to request that the test continues beyond the minimum, most are content to achieve the ‘gold standard’ of Keymark.

So how well does a single test to 1,000Pa cover us in the UK? 

In assessing that a structure has sufficient resistance to wind, Eurocode 1 requires you to apply a partial safety factor to the tested strength.  The safety factor you choose depends on how the solar panel fails.  For example a solar panel that has its failure in a metal component has a lower safety factor (divide by 1.1) than one where the failure is in wood (divide by 1.44).  This is to take into account the natural variability in the strength of wood and the consistency in the strength of steel. 

Since Keymark doesn’t require a test to find the failure level, there’s no way of knowing if the panel would have failed at 1,001Pa or would have gone on to 5,000Pa.  You also don’t know what the failure mode would have been.  Unless the manufacturer has tested beyond 1,000Pa the only safe assumption is to use 1,000Pa and, if they haven’t tested to confirm the failure mode, to reduce this by the highest partial safety factor of 1.44 for failure in a timber fixing.

Consequently, to be in compliance with UK Building Regulations and MCS, a panel tested to only 1,000Pa should not be used if the calculated wind pressure is higher than 694Pa, being 1,000Pa divided by 1.44.

I ran the wind calculator for the common situation of a two storey building with a duo-pitch roof at various wind speeds.  I assumed that flat plate solar panels are fixed above the roof in a position to avoid the edge-zones (which have higher wind loads), that the building location was 75m in altitude and relatively close to but not right on the sea (2-20km) and that there were no special topographical features (the building is not on a hillside).

It turns out that it’s really rather easy in the UK to achieve wind speeds that produce uplift pressures exceeding those for Keymark tested products.  The table below shows the calculated wind pressure (including partial safety factor) and the map summarises the results.

Some solar manufacturers will to tell you to just put a few extra fixings on if the winds are high.  A few moment's consideration reveal this is completely inadequate.  If you haven’t tested to failure, you cannot know that the fixings are the weakest part.  It could just as easily be the cover glass that comes away at 1,001 Pa.

The only installation that meets building regulations and therefore the requirements of the MCS installation standards is one that uses solar panels and fixing kits that have been tested to a level that exceeds the wind pressure.

It is a welcome development that the new test method in ISO9806 is to 2,400Pa, though it is regrettable that the authors of the standard did not take the opportunity to resolve other shortcomings of the wind pressure test that I have written about before.
 
I don't anticipate that many products will struggle to achieve this higher pressure level, after all people have been installing all over the UK for years.  The fact remains that until they’ve been re-tested to a higher wind pressure there will be many locations in the UK where the Keymark alone falls short of the mark as far as building regulations are concerned.  The responsibility is clearly with solar installers to use solar panels with a tested pressure resistance high enough for the location.

Slow Burner - how will the Domestic RHI Take off?

How much can the first year of the Feed in Tariff tell us about uptake for the Domestic RHI

How it went for the Feed in Tariff

A number of people (including the solarblogger himself) tried to temper expectations for the domestic RHI with the argument that the Feed in Tariff (FIT) took a bit of time to get going. The logic goes that it takes time for the public to become aware, for installers to work out how to market it, and especially for housing associations to get organised. 

I thought I'd take a look at the numbers to check whether they supported this idea. 

I wanted to compare the take up of PV in domestic installations before and after the introduction of the FIT. There is a wealth of data available from the Department of Energy and Climate Change (DECC) on the levels of PV deployment  under the FIT, but much less for the years preceding it. I relied upon this report on the Low Carbon Building Programme (LCBP) to build a picture of deployment rates before the FIT. 

Under LCBP phase 1 (the domestic stream) there were 4,428 installations of PV. The average size was 2.18kWp, for a total capacity installed under the scheme of 9.7MWp. 

Since the report doesn't disclose the deployment in each period, I estimated PV deployment based on overall scheme expenditure.  I then combined this with FIT data for systems below 4kWp, most of which is likely to be domestic. 

The results are very interesting. 

When you look at the plot of the overall data, it sure does seem that all the action started in year two of the scheme. But this is a trick of exponential growth. Look at the lower plot, where I have shown the data only up to the end of year one. The first year was spectacular. 

The level of deployment grew from round 700 installations a quarter before the FIT to 11,000 a quarter at the end of the first year. Before the FIT subsidy, solar thermal systems were being installed at a rate around 10 times higher than solar PV. By the end of the first year, solar thermal had declined slightly, but solar PV installations outnumbered them by almost double. 

And so to the Domestic Renewable Heat Incentive

There are a number of reasons why the domestic Renewable Heat Incentive won't take off like the Feed in Tariff did. 

1.  The Feed in Tariff.  

When the FIT was launched it was the only show in town. The grant scheme for renewable heat was derisory by comparison. As the domestic RHI launches, people interested in investing in their homes to reduce energy bills have the choice of both FIT and (I suppose) the Green Deal. 

2.  Installation complexity. 

With the exception of solar thermal, all the domestic RHI technologies replace an existing heating system, rather than being an add-on. People will be more cautious about installing a new technology when they worry that the impact of it not working is a cold house and no hot water.

Renewable heating installations are generally more intrusive too. A heat pump may require the replacement of radiators to cope with lower heating temperatures, biomass boilers can require a lot of space. New products such as this one which simplifies the installation of solar thermal to levels approaching that for solar PV may help overcome this barrier, at least for solar thermal where there's always the backup heater. 

3. Off Grid Target Market

The domestic RHI tariff levels were intended to stimulate a market in the 20% of homes that are off the gas grid. For sure, the returns are better when heating with oil or electricity, but returns for solar thermal on gas can also be good, as this analysis has shown. 

4. World First

The UK feed in Tariff followed the implementation of similar schemes in other european countries. Businesses could see the rapid take up of markets that had resulted and anticipating a similar trajectory for the UK, were pumped and ready once the scheme launched. By contrast the RHI this a genuine worlds first. There's no equivalent to look at to predict uptake. The many, many false starts for the scheme also didn't help. Many installation companies I spoke to weren't even willing to spend time thinking about it until they were absolutely sure it had launched. 

5. The Feed in Tariff (again)

My final reason is perhaps the most important. The way the government managed the Feed in Tariff has led to the widespread belief that as soon as any renewable energy scheme is successful it will be ruthlessly hacked back. The shadow that the treatment of the FIT scheme casts is long and pervasive. 

For all this, the scheme offers a level of financial support beyond anything that renewable heating technologies have benefitted from before. My plea to the industry is to give it a while before judging the success or otherwise of the scheme. 

It may take time to take some time to warm up, but warm up it surely will.  

The Domestic RHI and Solar Thermal Stores

The Law of Unintended Consequences Strikes Again

The domestic RHI was structured with the intent that the complementary combination of solar thermal with other heating technologies would be actively encouraged by receiving double subsidy for the domestic hot water energy.  Unfortunately, the wording of the legislation has prevented installers using the simplest way to implement a combined system (the thermal store) because it rules out solar systems that can make even a theoretical contribution to space heating.

Thermal Stores in Hot Water

Solar thermal systems can make a contribution to space heating as well as domestic hot water (DHW) preparation, especially in spring and autumn where the days are still bright and there is a demand for space heating.  These systems are not yet as common in the UK as those for domestic hot water, but in more developed European markets such as Germany and Austria, so-called "solar combi systems" are popular.

In a thermal store the domestic hot water is heated in a heat exchanger
and the contents of the store pumped around the space heating circuit

A good way to combine solar thermal with space heating is to use a thermal store, essentially a large (typically 500 litre minimum to 1,000 litre) hot water cylinder with heat inputs from both solar and the backup heating system and with outputs to domestic hot water and space heating.  Typically the body of water in the thermal store is heating system fluid (primary water) and domestic hot water is heated on-demand in a heat exchanger as it flows to the hot tap.

Both heat pumps and biomass heaters operate well when running continuously rather than cycling on and off, so charging a thermal store is a good technical solution that improves the overall efficiency of the heat pump or biomass boiler.

Where the designer is seeking for the solar to make a reasonable contribution to the space heating, the solar panel array installed is large (around 12-18 m² for a domestic property).   The coverage of domestic hot water of such systems can be very high, 70% and above.

Where the designer is aiming for solar to mainly cover domestic hot water the panel array is smaller (typically in the range of 3  - 6 m²).  In this case there is still a theoretical possibility that the solar energy will contribute to the space heating, though in practice the system is sized with the aim of supplying 60-70% of water heating.

The current domestic RHI legislation completely excludes systems that can contribute towards space heating.  

The text in the RHI regulations defines an eligible solar system as follows:

a)     is designed and installed to provide heating solely to a single eligible property and solely for an eligible purpose using liquid as a medium for delivering that heat;

(b) meets the requirements set out in whichever of the standards for solar thermal plants specified in paragraph 1(5)(a) and (b)“eligible purpose” means, in relation to heat generated by— […](b) a solar thermal plant, the purpose of domestic hot water heating for an eligible property;

An implementation of solar where there is even a theoretical possibility of the solar contributing towards space heating is completely excluded from the scheme.

The reasoning behind ruling out solar space heating was that the domestic RHI is “deemed” – the solar energy is not measured, instead it is estimated using an approved calculation and the calculation only works for domestic hot water.

However, by ruling out any solar installation that does not solely heat domestic hot water, the domestic RHI has made the combination of complementary renewable heating technologies such as solar and heat pumps less likely. Solar thermal has lower associated carbon emissions than any form of back up heater, so every unit of solar thermal heat that can be used, whether for space heating or domestic hot water reduces carbon emissions.

Configurations where the solar is offsetting a proportion of fossil fuel space heating are also disincentivised by their complete exclusion from the domestic RHI.

When installing biomass or heat pumps with a thermal store, the additional cost to add a solar coil into the store is very low, making the marginal cost of adding solar thermal more attractive.  The domestic RHI would provide greater value for money if it encouraged, rather than discouraged such systems.

So how could the domestic RHI be changed to include solar space heating?

Two Suggestions

Two options occur, though I’d be pleased to hear of any other suggestions (please use the comments section).

First, it would clearly be possible to use a heat meter to measure the solar input into the thermal store.  Solar space heating systems cost more than solar systems aimed only at domestic hot water.  A requirement to fit a heat meter would be a relatively smaller proportion of the total installed cost and energy benefits, and houses that can fit large thermal stores are relatively thin on the ground, so it wouldn’t be too much of a cost for the scheme administrators to deal with the meter readings.

A second approach would be to allow space heating systems onto the scheme but to give RHI payments only for the domestic hot water energy provided, and calculate this with the current deeming method.  I’ve looked at this with the help of two years'  of data from a solar space heating system provided by Geoff Miller of GreenLincs Energy.  Simulations have also confirmed that the solar energy generated by a system providing solar space heating and domestic hot water is always higher than the same sized system targeted at only domestic hot water.  The RHI wouldn't be over-paying for solar heat.

The best outcome would be for it to be the choice of the homeowner whether or not to go to the expense and hassle of having a heat meter.  If they wanted the extra payments for space heating, then they would need to install a heat meter, otherwise they could claim for only the solar heat in their domestic hot water.

This has formed the basis of a proposal submitted to the Department of Energy and Climate Change (DECC) yesterday outlining how the scheme could be improved by allowing solar space heating.

Replace or Refurbish?

What to do with older solar heating systems 

It could be so much better



I've been getting correspondence from solar installation businesses asking what the domestic RHI might mean for older solar systems, specifically ones that were never entered onto the Microgeneration Certification Scheme (MCS) when installed.  Is there any way for these to claim the Domestic Renewable Heat Incentive (RHI)?

Can you just inspect that the solar heating system is compliant with the current MCS scheme, re-commission it and register it as if you've just installed it?

Do you have to rip it out and put in a whole new one?  Would even this be allowed on the scheme?

Setting aside the fact that the intent of the dRHI was to stimulate new installations of renewable heating, and that finding a way to register an existing (and potentially working) system is not really in the spirit of things, let's have a look at the regulations and see what they have to say about it. 

MCS

A review of the MCS standards (MIS3001 and MCS 004) finds that they are silent on whether the equipment used when installing a solar system must be brand new to be registered with the scheme. The implication is therefore that an installer could go through the standard line by line to ensure that the existing installation is compliant, making changes to components as required and registering the system on the MCS database.  In effect the installer is building a system from ‘second hand’ parts, some of which happen to already be on site and fixed in place.

However, just getting MCS registered does not mean you can get the domestic RHI.  It's also necessary to comply with the eligibility requirements of the RHI scheme itself.

Domestic RHI

The domestic RHI legislation has now been laid in parliament, so it’s possible to see the basis that OFGEM will be using to create the scheme rules.

The relevant section of the domestic RHI regulations is on page 12 in section 9:

Plants used to generate heat before the first commissioning date9.—(1) The requirements referred to in regulation 3(b) are that no part of the plant which generates heat, other than any of the components listed in paragraph (2), was used before the plant’s first commissioning date.(2) The components referred to in paragraph (1) are—(a) immersion heaters and other components which solely generate heat for the purpose of heating domestic hot water;(b) supplementary electric heaters; and(c) circulation pumps.

From the above it seems that so long as the heat generating part of the installation is new, then other parts of the heating system can be re-used.  This makes sense – it would be crazy to insist that a new biomass boiler installation also had to replace all of the connecting pipes, radiators and hot water cylinder in the home.

In relation to a solar thermal system, the parts of the plant that can generate heat are:

1. Solar Collector
2. Pump
3. Immersion heater in cylinder

Items 2 and 3 are specifically excluded in the regulations.  It seems to me that to modify an existing solar thermal installation so that it is eligible to join the domestic RHI scheme, it is necessary to change the solar panels, but that all other components could be re-used.

Have I missed something?