SAP 10 - Big Changes Afoot for Solar

Image: Viridian Solar

A new version of the Government's Standard Assessment Procedure (SAP) for the calculation of energy use in dwellings has been published and it contains a number of changes to the way the impact of solar technologies is assessed. 

The key outputs of the calculation described in SAP are:

Dwelling Emission Rate (DER) - the carbon emissions from energy use to heat the house, provide hot water and power lighting, pumps and ventilation. It is expressed in kgCO2 per square metre of floor area per year.

SAP Score - a figure rating the energy costs normalised by floor area to heat the house , provide hot water and power lighting, pumps and ventilation. A house with a score of 100 has energy cost of zero each year, a house with a score of 0 has huge energy costs. The scores from 0-100 are divided into bands corresponding to EPC ratings from 'A' to 'G'

Fabric Energy Efficiency (FEE) - the space heating requirements for the dwelling in kWh/m2

Energy Consumption per Unit Floor Area - which can exclude plug-in appliances (as the above measures do), or include an allowance for appliances and electrical equipment.

Not Just for New Build

SAP is used to calculate the energy efficiency of newly built homes to meet Building Regulations. New homes must currently have a Fabric Energy Efficiency and Dwelling Emission Rate below a mandatory maximum.

Through Reduced Dataset SAP (or RdSAP), the calculation is also used to generate Energy Performance Certificates for existing properties. Over time the SAP rating of homes has become embedded in a range of government initiatives and incentives, for example EESSH in Scotland requires that all social rented homes in Scotland achieve a minimum SAP score by a certain date, and access to preferential Feed in Tariffs are linked to the house having an EPC rating higher than D.

What's Changed?

Carbon Intensity of Grid Electricity

The electricity grid has decarbonised with the move away from coal burning power stations and greater input from gas fired generation and from renewables (see my blog on this subject here). The proposal is to reduce the carbon intensity of electricity from 0.519kgCO2/kWh in SAP 2012 to 0.233 kgCO2/kWh in SAP10.

Discussion

This is a huge (55%) reduction compared to the current version of SAP, and lower than the figure consulted upon (0.398 gCO2/kWh). However, it is only a reflection of the huge progress that has been made in decarbonising the grid.

The impact for solar photovoltaics is that solar systems will need to be more than double the size of current systems to produce the same carbon benefit in the calculation, which could reduce the competitiveness of solar PV as a means of meeting building regulations. SAP10 will only be brought into use for the next update to the Building Regulations, and government will need to carefully consider whether it is now time to change the primary focus of the regulations away from emissions and towards energy consumption (like for appliances).

For example, emissions from mains gas will be 0.210kgCO2/kWh in SAP10. When you take into account efficiency losses from burning gas in a boiler to heat a house, developers will be able to achieve the same dwelling emissions rate using simple electric heating instead of gas - for example panel heaters and a hot water tank with immersion heater. It may be possible to remove the whole wet heating system and gas supply from new homes, yielding considerable construction and maintenance savings, but possibly saddling house buyers with unaffordable energy bills (unless, perhaps, solar is also fitted).

Export of Solar Generated Electricity

The value of exported electricity in SAP10 is 3.8p/kWh, whereas the cost of grid electricity is 16.6p/kWh on standard tariff. In SAP2012, exported solar electricity is assumed to be of the same value as electricity bought by the householder (which was dubiously justified by the existence of Feed in Tariffs - despite that in solar schemes for social tenants the tariffs went to financiers).

SAP2012 also assumed that 50% of generated electricity was used in the house (called the beta-factor) and 50% exported.  While this generally accepted assumption has started to look rather shaky as installed solar systems got larger, it didn't really matter because the value of exported electricity was the same as the saving made for energy not bought from the grid.

For SAP10, a more sophisticated treatment of the beta factor is used. The proportion of energy used in the house is now a function of the size of the solar system's energy output as a proportion of the energy demand. Larger solar systems attached to small energy demands will have a smaller beta factor and smaller solar systems attched to a large energy demand will have a higher beta factor. Adding a battery into the property will increase the beta factor.

PV diverters can also contribute towards energy for hot water in SAP10, so long as a battery is not present and the hot water cylinder has a sufficient volume (more than daily demand). 80% of generation, less the beta factor is available for input to the hot water cylinder, and the benefit is further diminished by a factor of 0.9 to take into account increased cylinder losses due to higher average storage temperatures.

Discussion

None of these changes affect the Dwelling Emissions Rate used for current building regulations. Solar PV saves carbon whether the electricity is used in the house or not.

These changes do, however, impact the SAP score and EPC band, as they impact on the calculation of the energy bills associated with the house.

The calculation of the beta factor was derived from a relatively small data-set, some of which was provided to BRE by the Solar Trade Association. An industry group is working to develop a much more comprehensive set of data to improve confidence in the value that SAP produces and to feed into the Microgeneration Certification Scheme guidance to solar / battery installers.

Shading

The PV shading penalty has been increased, that for solar thermal remains unchanged.

SAP2012 applies the following penalties to energy production - Modest shade 0.8, Significant shade 0.65, Heavy shade 0.5

SAP10 modifies as follows - Modest shade 0.5, Significant shade 0.35, Heavy shade 0.2
As an alternative the MCS overshading figure can be used.

Discussion

Industry were concerned about a complex two-step shading calculation process that was proposed in the consultation, and it seems that these concerns were noted, albeit with what look like penalty default values for systems with shading.

Hot Water Demand

A new, more complex calculation for domestic hot water demand reflects the growing importance of this area of energy consumption as increased insulation levels drive down space heating requirements. This is an area that the solar industry has been lobbying for change.

The new calculation takes into account the higher flow rates and lower inlet temperatures associated with the now more common mains hot water showers (either from pressurised hot water cylinders or combi boilers), when compared with header-tank fed systems.

Inlet temperatures have also been reduced for both header tank and mains fed systems as a result of input from the solar industry (by 2-3 degrees).

Discussion

I calculated a 10% increase in hot water demand for mains pressure fed systems compared to SAP2012. The decrease in inlet temperature will add a further 5% or so to the energy required to heat the water.

An increase in the assumed hot water energy will be welcomed by the solar thermal industry in particular, but higher general energy consumption will aid all energy producing technologies.

Solar Thermal Space Heating

In previous versions of SAP, solar thermal could only be applied to meeting hot water demand, which created an restriction on its potential contribution to household energy demands.

The Solar Trade Association proposed EN 15316-4-3 as a potential route to the inclusion of solar space heating in addition to solar water heating, and provided BRE with guidance and assistance in assessing the new method.

The published version of SAP 10 did not include details of the new method as testing was not complete at the time of publication, so the solar thermal appendix currently has holding text. I will be able to discuss more about how the new calculation works and the results it gives once the final version is revealed.

Discussion

The solar industry will welcome that SAP includes solar space heating. Less for the opportunities it brings in new build (where space heating demands are limited due to high levels of insulation), rather for the possibilities it opens up to improve the EPC ratings of existing properties with high space heating demand. The domestic Renewable Heat Incentive only supports solar water heating at present due to there being no approved method of 'deeming' (calculating) the expectd savings. The new SAP methodology will open up the enticing prospect of solar themal payments under dRHI linked to heat generated for both water and space heating.

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.

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.

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?

Domestic RHI Regulations Laid Before Parliament

58 Pages of Pure Reading Pleasure

The Regulations for the domestic RHI were laid in parliament yesterday, a significant step towards the imminent launch of the scheme. 

You can read them here:

As a result, some remaining points of clarification for solar thermal on the scheme have now been made public:
 

• Solar for space heating / indoor swimming pools are not eligible, in fact solar DHW is not eligible if it is combined with space heating or swimming pool heating.

• Air heating  (transpired) solar panels are not eligible.

• Hybrid PV-T panels are not eligible.

• The regulations refer to version 1.0 of the MCS deeming calculation (MCS024) and not the most recent version 1.1, this means that the MCS standard is immediately out of synch with the RHI and it omits the Incidence Angle Modifier from the deeming method, putting evacuated tube collectors at a disadvantage.

I suspect that the solar industry might be most aggrieved by the fact that a solar system that heats an indoor swimming pool is ineligible.  Setting aside the politics of envy, swimming pools are an ideal application for solar heating, the low temperature of the pool meaning that panels operate at higher efficiency than when preparing domestic hot water alone. 

Under the rules published yesterday, if a solar system is installed to prioritise domestic hot water with a divert to a pool once the hot water is satisfied, then the renewable heat for the domestic hot water is also ineligible.  This creates a perverse incentive to install the solar system as two separate systems, one for the pool and one for the hot water.

A simple way to deal with a complex system such as this would be to allow the owner to opt to meter heat rather than deeming it.

The scheme is not set in stone and there will be opportunities to amend it over time.  However, if the Department of Energy and Climate Change (DECC) is going to expend resources to do so, then the industry is going to have to build a strong case to support the argument that any prospective change is worth the cost and trouble. 

Should any of these omissions from the scheme concern us?  What do you think? 

 

 

 

 

What does Energy Cost?

Where can you find authoritative data on energy prices?

The energy savings from solar heating is the main economic argument for choosing to install a system, and this will continue to be the case even with the imminent arrival of the domestic Renewable Heat Incentive in the spring of next year.  For solar PV systems the fall in cost of equipment and installation and the accompanying reduction in the Feed in Tariff means that own-use savings on electricity bills have become a much more significant component of the economic justification.

Energy prices have been changing rapidly, so it’s important for renewable energy businesses to have access to up-to-date, accurate and trustworthy price information to show to customers when modelling the financial benefits from their investment.

A quick survey of colleagues at a recent Solar Trade Association meeting produced the following list of resources.  Do you have any to add?  Please use the comments section below.

UK Government Statistics

There’s a wealth of energy statistics on the gov.uk website, and the challenge can be finding the information you want.

https://www.gov.uk/government/collections/domestic-energy-prices

By their nature, the statistics are backward-looking so often more than 12 months out of date.

Energy prices are often presented either as ‘average energy bills’ or stated as a percentage of 2005 costs.  The best source I could find was in the Quarterly Energy Prices publication, in which the following two tables show the unit price of energy:

Table 2.2.3 Average annual domestic electricity bills in 2012 for selected towns and cities in the UK with average unit costs

Table 2.3.3 Average annual domestic gas bills in 2012 for selected towns and cities in the UK with average unit costs

Sutherland

The Sutherland tables are a fixture of the energy industry, compiled quarterly since 1976 they show domestic energy costs heating and hot water costs across a range of standard house types across the UK.  The data is apparently used by government in preparing its own statistics, but there is a cost to accessing the data.

http://www.sutherlandtables.co.uk/

Boilerjuice

Boilerjuice.com is an online quotation website for heating oil.  It publishes average prices of UK heating oil:

http://www.boilerjuice.com/heatingOilPrices.php

Nottingham Energy Partnership

NEP publishes current average prices for electricity, gas, and heating oil together with many other fuels.  Also available are reports analysing trends over time.  This was the most relevant reference I could find for current energy prices.

http://www.nottenergy.com/energy_cost_comparison/

 

Do you know of any resources you can share?  If so, please let us know in the comments section below.

 

Information is Beautiful

Why the solar thermal industry should embrace data logging

by guest blogger Ben Whittle

Who is this person that the Solarblogger has invited to wax lyrical on the rather un-sexy subject of data that you have never heard of before, I hear you ask?

Some might say my claim of authority to write on this subject is sketchy at best: I’ve only lived with and monitored a solar thermal system for less than 6 months, and I have only seen data from a few installations ever. But maybe that is exactly why it is a subject that needs discussing in the solar thermal industry… because I have been installing and designing solar thermal systems for around 10 years and I can count the number of installations I’ve seen that have monitoring on them on one hand, (and one of those installations is my own). And when I say we need more data-logging, I don’t mean turning on the heat quantity measurement function, I mean proper data-logging: measuring temperatures at the top, middle and bottom of the store, pump on and off times, boiler trigger times, heat measurement, the lot.

Over all the years I have worked in this industry I have seen a lot of mistakes made in designing and installing systems (and some of them were my own mistakes). How do I know they were bad designs and mistakes? Because I had to go and fix them. How can we possibly move on as an industry if we can’t try and make some sense of what mistakes were made in the past, and learn from them? Of course we have made leaps and bounds in some areas: the quality of the panels, plumbing, tools and fittings we are using (thank the lord for press fit pneumatic tools and filling pumps!), the MCS standards, the list goes on. OK, great, we can install stuff quickly and efficiently and it doesn’t leak… what’s the next step? Actually measuring how the systems are performing. Because I can tell you in the UK we have a long way to go in terms of getting our solar thermal systems to perform as well as can be achieved as seen across mainland Europe and America , and keeping track of performance is the only tool that can help us do it.

Now of course there are all sorts of reasons as to why we don’t normally achieve performance levels of a high quality Austrian installation… predominantly that is because the average UK house doesn’t have space for a 500-1000litre hot water store in the 700mm wide airing cupboard. But let’s put aside the things we can’t tackle and talk about the things we can.

To my knowledge there are only 2 or 3 solar thermal trials of any significance that have been published in the UK on solar thermal, and probably the best of these was conducted by the Energy Savings Trust three years ago. For those that are interested it’s called “Here Comes the Sun – A field trial of solar hot water systems”. It’s a great document, short (24 pages) and to the point. It tells you what you need to know – the biggest impact on solar thermal performance has nothing to do with evacuated tubes or concave reflector plates or low emissivity glass. But how did they reach those conclusions? By measuring things and writing it down – and, you know, analysing it and stuff.

And that is where we need to be going as an industry – looking at data, working out how to improve things, and changing our behaviour to suit. Not only will measuring performance allow us to understand the mistakes we make, it can inform our design decisions and help us to improve everything we do… and of course there are other benefits to consider as well.

1: Data logging is another chance to “add value” to your installation work. It’s a slightly more expensive controller, or an additional bit of kit to be sold, and a chance for your geekier clients to play with a spreadsheet or two. Now if you haven’t had a great experience installing solar thermal and the thought crossing your mind right now is “yeah right, and the customer is going to use this data to beat me with like a stick when it all goes wrong,” then I really am talking specifically to you. Because there are thousands of systems out there in the world that do perform absolutely perfectly, and as an installer you need to understand how they work.

2: It’s a chance to fault find, and take the correct action if things do go wrong, instead of guessing.

3: It will help you understand how people interact with their solar systems.

4: It can help get you out of trouble if the cause wasn’t your fault. One of the few logged systems I have seen was a school pool system that was constantly stagnating and losing pressure after being installed. When the data card was posted back to the company I worked for, it didn’t take long to diagnose the fault. The college maintenance man had been turning the system off at the main switch on a regular basis (even though it had a sign on it saying “Solar – do not switch off”). We were even able to re-program some of the settings using the data card and send it back to them in the post to plug back in. That’s quite an unusual feature specific only to the controllers made by Watts industries as far as I know, but a pretty handy one for commercial systems.

Just imagine what could be possible if we all took this a bit more seriously – imagine coming in to your office on a hot summer day in a few years from now after installing a 1000 systems across your local area, to find a couple of automatically generated emails where your data server had logged some de-pressurisation warnings at a couple of properties. You could then log on to watch some live system data to check them, and dispatch a maintenance team to fix them before your client was even fully aware there was a problem. All part of the regular maintenance contract you sold them at the time of installation…. There is no reason why this fantasy couldn’t come true, and it’s up to us to make it happen. It is already happening in the world of heat pumps.

As an aside, maintenance contracts are another area I think we need to explore further as an industry. I recently saw a report suggesting a very significant proportion of people who buy solar thermal systems would be happy to pay more than £100 for regular servicing, another possible revenue stream for any installation business.

Red=panel, Yellow = top tank, Blue = mid tank, Grey = low tank

R1 = solar pump on, Rs = boiler on

My own system does not have anywhere near enough data yet. I’m currently measuring temperature at 3 heights in the store, the solar controller also controls my boiler so I can also measure how frequently the boiler is getting activated, and I’m also getting estimated energy yield using the heat quantity function on the controller and estimated flow rates. In an ideal world I hope to add a water meter to measure my hot water usage, and a proper electronic flow meter for the solar controller to measure the glycol flow rates, and an electrical meter to measure electrical consumption. But I must be doing something right because I am currently hitting 2100kWHours of energy from my installation, after being installed for less than 6 months. And thanks to the EST solar study I know that the average UK installation is usually generating 1500kWH in a whole year… and I would never have found that out if I hadn’t bothered to log the data. Of course that generation figure could be inaccurate, and I mean to find out if that is the case by getting more and more accurate data over time.

I should probably qualify that performance figure by pointing out that I do not have an “average” UK system, so I’m comparing apples with pears… but I hope to explore that issue in a further blog post, looking into hot water storage, and how we might start improving solar thermal performance in the UK.

 

Let's Get Down to Brass Tacks

How to Sell Solar With the RHI

 

The shape of things to come?  Solar heating and solar PV in a combined installation.
Image courtesy : Viridian Solar

Perhaps inevitably, the first reaction of the solar industry to the new domestic Renewable Heat Incentive (RHI) has been to compare the financial returns for solar heating to the Feed in Tariff (FIT) available for solar photovoltaic panels.

A quick, back-of-envelope comparison is not normally favorable to the RHI, but a more considered evaluation raises some interesting points.

So, before you screw up your envelope and toss it in the bin, read on…

Wide Applicability

Solar water heating requires a much smaller area of roof than PV.  An area of 3 or 4 square metres (2-3 kWth) is ample for most households.  The average PV installation according to the Energy Saving Trust has reached 3.75 kWp or around 22 square metres.  Solar heating therefore is more useful for partially shaded roofs, where only a small part of the roof area can be used.

Because it takes only a small portion of the roof, it can also be more palatable for customers who are interested in the impact of the solar installation on the looks or re-sale value of the home.

The RHI will require only loft insulation and cavity walls to be filled, and only where it is practical to do so.  This means that any building can qualify at modest cost.  The FIT is limited to homes that can achieve EPC D, and many cannot except at exceptional cost. (I’m expecting the FIT to migrate towards similar qualification criteria to RHI – watch this space).

Solar heating is also less affected by orientation or the location of the installation, with a lower drop-off in energy yield for east or west facing roofs or installations in the north of the country.

These factors all contribute to a large potential customer base for solar heating.

Sweet Spots

As the Feed in Tariff (FIT) rates have fallen, energy savings start to feature more and more highly in the financial returns calculations.  Solar companies are starting to get used to the idea that the financial returns for PV now depend much more on the customer’s patterns of energy use and therefore the sizing of the system.  (See my blog on self-consumption of solar electricity here.)

The Renewable Heat Incentive for solar is set at a level where the return on investment also relies upon the amount of energy saving the customer achieves.  This creates “sweet-spots” with above average financial returns:

Larger families

On average, the more people in the house, the more hot water the household uses for showers and baths.  The same solar installation will produce a greater annual energy output when there’s more cold water to be heated up, and the MCS deeming method captures this.

Oil or electric heating

The more expensive the heating fuel being saved, the better the returns that are achieved.  Off gas grid installations will have a higher return on investment.

Cost Sharing

Installing solar heating at the same time as other necessary work can transform the return on investment.  The installation of a solar cylinder can be as much as one third of the cost of the installation.  If a customer was planning to replace an old hot water cylinder anyway, then going solar at the same time would make a great deal of sense.  The same argument goes for roofing repairs, where roof access costs can then be shared.

Rather than relying on chance to provide opportunities for cost sharing, the solar industry now has a gold-plated opportunity to create its own.

From “Either-or” to “Both-and”

A solar installer can create cost sharing to boost the return on investment for customers very simply.

Create your own sweet-spot by offering to install both solar PV and solar heating together. 

The shared costs of travel, roof access and roofing works provide obvious cost reductions, but it goes much further than that.  Because the average sales price per install is boosted the costs of customer acquisition (sales and marketing, survey) are also shared across more revenue.

Counting All the Pennies

When preparing a financial calculation for solar water heating there are a couple of important points that are easy to miss out.

First, the saving on the energy bill is not the same calculation as the solar energy added to the hot water cylinder.  The fuel burnt to create the same level of heat is higher because the back-up heater will operate with efficiency below 100%.  In fact, it gets better because the “summer efficiency” of boilers is lower than the “winter efficiency” because they have to heat up just to prepare the domestic hot water.

The new version of MIS 3001 proposes a range of “solar efficiencies” for different back up heaters, but a few of the more common ones are shown below:

The energy saving is the solar energy input to the hot water cylinder divided by the boiler efficiency.  Depending on the efficiency of the back-up heater in the home, the fuel saved can be as high as double the solar energy.

Second, the customer is getting a brand new hot water cylinder as part of their solar installation.  If it’s replacing an old cylinder with lower performing insulation and if it’s carefully installed with insulation on all the connecting pipes (not just the solar ones), then there is a significant energy saving for the customer.  When replacing an old cylinder with a properly installed new one, the energy saving averages 750kWh/year, adding around 50% to the energy saving.

These savings are real and they are significant, they should be taken into account in any presentation of the financial benefits of solar heating. 

Getting Emotional

The solar PV market has spent the last few years selling a financial product.  Cold, rational arguments about return on investment, fuel price inflation and comparative returns from ISAs have crowded out the emotional reasons people still have for buying into renewable energy: energy independence, climate protection, conveying their values to others.

Solar heating and solar PV top the charts as the renewable technologies most people know about and understand.  This is especially true for solar heating.

When you step under a hot shower provided by a solar heating system, you are provided with an intuitive, physical link to the energy you are producing.   A customers’ relationship with solar water heating is intimate and emotional.

After all, which other renewable energy technology do you get naked with?

People are not cold, profit-maximising robots - they are individuals with a wonderful capacity to  surprise. The solar industry needs to re-connect with all the emotional reasons for installing solar – oh, and by the way it makes great financial sense too.