RefurbN16

Tag: Microgeneration

  • Solar Water Heating Trial Results

    The Energy Saving Trust has published the results of a solar water heating trial. There are some interesting findings which I’ve excerpted here:

    Summary of key findings

    1. Solar water heating systems have the potential to work well in the UK and the Republic of Ireland when installed properly and controlled adequately by the user.

    2. From the properties we trialled, well-installed and properly used systems provided around 60 per cent of a household’s hot water. The trial also found examples where systems were not properly configured or used, and where the contribution from solar was as low as 9 per cent. The median across all systems was 39 per cent.

    3. Householders in the trial were happy with their solar water heating systems: 84 per cent were “satisfied” with their system, and over 50 per cent were “very satisfied”.

    4. In the field trial, there was little difference between the total solar energy yield of those installations that used flat-plate solar collectors and those that used evacuated-tube solar collectors.

    5. The trial found that the way householders use their solar water heating system is critical in achieving the best results from solar water heating systems. Better advice to users on how to control their solar water heating systems (in terms of volume of hot water use, timing of back-up heating and hot water use, and temperatures required) is essential.

    6. Where mains electricity provided power to the pumps and controllers of systems in the trial, the amount of energy used was generally small compared with the overall heat delivered.

    7. We observed insufficient insulation installed on some hot water storage cylinders and pipes. This significantly reduced the proportion of hot water their solar water heating systems provided.

    8. Industry standards should be reviewed to ensure they reflect the findings of the trial and the need for better advice to customers.

    9. Solar water heating systems can achieve savings on energy bills. Based on the results of the trial, typical savings from a well-installed and properly used system are £55/year when replacing gas and £80/year when replacing electric immersion heating; however, savings will vary from user to user.

    10. A well-installed and properly used solar water heating system is likely to provide carbon savings. The typical savings are 230kg/year when replacing gas and 510kg/year when replacing electric immersion heating.

    If you’re thinking of going for solar water heating then it’s worth checking out the report. EST also published a similar report on their heat pump trials a while back.

    Renewable heat sources are expected to be supported by the Renewable Heat Incentive (which will be similar to the Feed In Tariff for electricity generating microgen) but there have been many delays to its launch and it is currently uncertain exactly when it might come into effect.

  • Solar Thermal Systems – Part 1

    A couple of weekends ago a group of us went to see a very interesting solar thermal installation in Stoke Newington. Generally, solar thermal systems supply heat for hot water only, but this system did a lot more than that as it was also plumbed into the heating system.

    I’ll go into more detail on this particular system in a second post later this week, but first up we have a little overview of solar thermal technology…

    Solar water heating systems are the most common form of microgeneration (small scale renewable) technology in the UK and Europe. This technology has been around for quite a long time (since the 1970s in this country), quietly generating heat in sunny weather to make a significant contribution to a home’s hot water energy consumption.

    Naturally they perform best in the sunniest summer months, when virtually all of your hot water needs can be supplied by a good quality installation. Even during the winter months, a sunny day can result in a substantial amount of hot water being generated.

    It is worth noting at this point that hot water energy consumption comprises around a quarter of a typical home’s total energy needs. Space heating uses the lion’s share, making up nearly 60% of total consumption. So a solar thermal system that only supplies hot water won’t cut your total energy consumption drastically, but it does make a good contribution.

    Harnessing heat from the sun is, in essence, very simple: a collector is mounted on a south facing roof, absorbing the heat from the sun’s rays. The collector has a network of pipes through which a fluid passes, warms up and then takes the heat to a water-filled cylinder for storage and later use. There are two types of collector: flat plate and evacuated tube.

    A flat plate collector is the simpler of the two, consisting of a glass covered heat absorber with pipework passing through it. This type of collector is the cheaper of the two, but it is also less efficient so harnesses less heat for a given area of collector.

    Evacuated tube collectors consist of an array of glass tubes with copper strips running along the middle. The glass tubes have had the air removed from them which reduces losses due to convection and conduction and allows them to reach higher temperatures than flat plate collectors. This means that they offer better performance, absorbing more heat for a given area of panel,  but they do cost a bit more.

    The fluid passing through the collector is usually water mixed with a form of antifreeze, along with a chemical that reduces corrosion. This fluid is kept completely separate from the hot water that comes out of your taps.

    Apart from the collector, you’ll also need somewhere to store all of this lovely heat and a conventional hot water cylinder won’t be enough.

    The most common solution is  to fit a twin-coil cylinder which has one coil in the lower part of the cylinder fed from the solar water heating and a second coil in the upper half of the cylinder which is fed from the boiler. The solar thermal system therefore supplies as much heat to the water as it can when the sun is out and then the boiler tops it up with additional heat as necessary.

    This need to store heat means that combining solar water heating with an combination boiler can be tricky (although it is possible) because the space for a decent size cylinder will most likely have been given up for other purposes. If you are ever considering removing your hot water cylinder and opting for a combination boiler, consider whether you might want to fit solar thermal at a later date.

    As ever, when considering microgeneration technologies make sure that you’ve gone as far as reasonably possible in terms of reducing your energy demand first. Ideally you should reduce demand as far as possible before considering generating because for the most part it is much more cost effective to reduce energy consumption than it is to generate.

    The Energy Saving Trust has a good publication on solar water heating which gives a more detailed overview of the technology, but it only goes as far as using solar thermal for water heating. The system we saw was also plumbed into the heating system, allowing the user to make use of much more of the heat falling on the roof.

    A system that just heats the hot water can only go so far because you only use so much hot water (unless of course you are particularly partial to baths). If you have lots of sunny weather the panel will keep generating heat and that heat has to go somewhere. Being able to deliver it to radiators or an underfloor heating system is a real bonus.

    I’ll post more details about this fully integrated system later this week.

  • Sustainable Refurbishment – Towards an 80% Reduction in CO2 Emissions

    The UK’s building regulations didn’t start to consider energy consumption until the 1960s, when very basic requirements to conserve energy were placed on house builders. These requirements have slowly been tightened over the decades and the introduction of the Code for Sustainable Homes has accelerated this in recent years.

    The intention is that new build homes built from 2016 will be zero carbon (although the exact definition of ‘zero carbon’ in this case is still up for grabs). The problem is that the UK’s housing stock is the oldest in the developed world, with 8.5 million properties over 60 years old and an estimated 24 million homes built up to 2016 expected to still exist in 2050.

    Zero carbon new build homes are definitely needed so that new homes don’t add to emissions, but all of the carbon reductions will have to happen in homes that have already been built.

    In the previous post we looked generally at a whole house approach to sustainable refurbishment. The Energy Saving Trust has recently published an interesting new publication which looks at this in more detail and points the way towards an 80% reduction in CO2 emissions in existing homes. This guide is aimed at homeowners as well as housing developers and builders and is clearly written and nicely presented.

    It gives an excellent overview of the energy efficiency measures that can be implemented in the UK’s homes including the different types of wall, roof and floor insulation, improving windows and doors, increasing air tightness as well as efficient heating and hot water systems and lighting and appliances. Also covered are microgeneration, water efficiency, waste and recycling and even climate change adaptation.

    If you want to get a good picture of what needs to be done to our homes, then this is a good starting point. Hopefully it will stimulate you to consider which of these measures can be applied in your home.

    The Energy Saving Trust has lots of interesting technical guidance. More information can be found here.

  • Details of UK Feed In Tariff Announced

    The overdue announcement of the UK’s Feed in Tariff (FiT) is at last being made by Ed Miliband today, ending a period of uncertainty for the UK microgeneration industry. FiTs have, for the most part, been hugely successful in a wide range of countries around the world and their introduction to the UK is long overdue.

    The good news is that it’s looking better than expected; it’s certainly better than the rates proposed in the consultation.

    The key to the success of FiTs is that they offer security to people considering making the leap into the microgeneration world. The UK FiT will be have a lifetime of 20 years (25 years for solar photovoltaics) and should mean you can make a return of about 8% on the investment, considerably better than what any bank will offer!

    The UK FiT will pay a fixed incentive for every unit of renewable electricity generated by microgeneration systems, whether the electricity is used on site or exported to the grid. The rates paid (detailed here) will vary depending on the technology and the size of the system.

    For retrofit solar photovoltaic installations up to 4kW, the initial rate will be 41.3p/kWh (about 5p/kWh higher than the rate put out for consultation which is very good news). The average size of a residential PV installation is about 2kW to 2.5kW. Rates for larger PV installations are lower presumably because economies of scale will start to kick in you’ll get a lower installation cost per kW.

    Small wind turbines are also eligible but not recommended in urban locations, along with micro hydro (probably a bit tricky in N16) and anaerobic digestion (ditto).

    The announcement also includes details of the Renewable Heat Incentive (RHI) which is due to be introduced next year. My reading of the press release is that solar hot water will get 18p/kWh but that’s so high I can’t believe I’m reading the table right.

    The FiT rate that an individual receives will be constant over the FiT lifetime but for some technologies the rate will reduce for later entrants, so the later you get involved, the lower the FiT paid over the lifetime rate will be. To illustrate, if you buy a PV installation this year you will get 41.3p/kWh, if you buy it in the third year you will get 37.8p/kWh.

    On top of the FiT, any electricity you export to the grid also has value. The consultation was proposing to fix the export tariff rate but I can’t see any evidence of that in this press release, but you can search for the best export tariffs on the Energy Saving Trust’s website.

    More good news is that the FiT will apply to installations made after July 2008 rather than July 2009 as proposed in the consultation. This is good because it means that some of the early adopters won’t be penalised for being ahead of the curve, although many will. (see update below)

    Of course these things don’t come for free though and the cost of the FiT will be shared around all households, with the levy expected to be around £10 per year per household.

    This is a fantastic incentive which will give the UK microgeneration industry a much needed boost, however you should really have done everything you can to lower your energy demand before opting for microgeneration technologies. Look at your home’s electricity consumption, insulation, air tightness and boiler efficiency before looking at microgeneration.

    Updates:

    • It turns out that the DECC press release has a typo in it and installations made before 15th July 2009 will be ineligible for the FiT. Details can be found in point 179 of the Government’s Response to the FiTs Consultation.
    • The export tariff has been reduced from the proposed 5p/kWh to 3p/kWh
    • FiTs and export tariffs will be indexed to the Retail Price Index so they will rise with inflation.
    • FiT income from domestic installations will not be taxable for the purposes of income tax.
    http://www.decc.gov.uk/Media/viewfile.ashx?FilePath=Consultations\Renewable%20Electricity%20Financial%20Incentives\1_20100201131016_e_@@_GovernmentResponsetotheFITsConsultation.pdf&filetype=4

  • Queen Elizabeth’s Walk Pt 1

    One of the Building Group members, Yvonne, kindly hosted a well attended Buildings Group meeting last night, which included a couple of new faces.

    Her home is a south facing Victorian mid terrace with suspended timber floors and rooms up in the loft. It’s located on Queen Elizabeth’s Walk up near the reservoirs north of Lordship Park.

    Yvonne and her partner will be building a wider extension, amongst other work, and recognised that this would be the perfect opportunity to overhaul the rest of the home’s energy efficiency. They took a trip to the Centre for Alternative Technology in Wales where they received some excellent advice and had the opportunity to get up close and personal with a wide range of high performance building materials and technologies.

    The main energy efficiency work which they will be undertaking is challenging.

    The dormer roof has all sorts of angles and slopes which make insulating difficult. Multiple materials of varying thicknesses will be needed, but the important thing is to ensure that there is a continuous “tea cosy” (as Fran puts it) of insulation on all surfaces, even if it’s just a modest amount on some surfaces and more on others.

    The suspended timber floor needs insulation but has Parquet over the top which means that taking up the floorboards is not possible. Access to the space underneath the floor is very tight across much of the floor area so this could prove a bit of a headache, but there are options which we will cover.

    Yvonne is also looking at fitting microgeneration technologies. With the south facing roof, solar hot water and photovoltaics are clearly strong contenders. The feed in tariff is being introduced in April, which makes this a good time to be considering electricity generating technologies, but as always with microgeneration, you need to ensure that your energy consumption has been reduced as far as practicable before investing, which is exactly what Yvonne is doing.

    Update: Yvonne has started a blog charting her progress.