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Salvaging Solar Investments

For more than a decade at the start of the 21st century, the Government drove efforts to explore the validity of solar renewables; first solar photovoltaics for generation of electricity, and later solar thermal as a means of capturing solar energy onsite for water heating.

Purchasing flat plate or evacuated tube systems proved cost-effective, and the technology enjoyed a hey-day with many school buildings employing one or both options.

Nearly 15 years on, many of those systems now sit unusable on the roofs of those buildings. The causes are varied; poor initial installation issues and particularly a lack of servicing and maintenance ultimately lead many systems to overheat and fail, even sealed systems. Manufacturer support for evacuated tube systems also waned as key suppliers moved away from the technology. Some sites suffered from costly vandalism. For many schools, the costs of protecting an installation or repairing it were too high and they were simply switched off and written off as a loss.

Solar technology did not die though. Properly installed and serviced solar thermal systems prove to have a long operational lifespan with low maintenance demands, especially flat plate collector systems. Those with proven drainback technology employing gravity flow to preserve operational qualities of the solar fluid required to transfer solar energy as heat to the hot water application are notably robust.  A well-designed and balanced hot water system deploying solar thermal as a preheat can offset a minimum of 30% of the annual energy demands for hot water in the UK. For some regions, this percentage is much higher and in the summer months, solar can meet all a system’s heating demands, especially in the case of buildings with lower daily hot water demands such as offices and classrooms.

The drive for net zero has also helped reinvigorate interest as education is challenged to transition from gas to electric water heating. As grid electricity continues to be substantially more expensive than gas (by a factor of 5.5 at the close of 2023) the energy bill shock from transition for many has meant technology that can offset electrical energy usage is becoming more attractive. The return on investment (ROI) for solar thermal is once again powerful, with systems able to pay back capital investment in under 10 years.

The New Rooftop Battleground

Chillers, heat pumps and solar systems are all vying for valuable rooftop space as schools look to reduce carbon emissions and embrace high-efficiency heating and cooling. We would always advocate splitting solar water heating (solar thermal) from solar space heating (PV) to gain the greatest efficiencies. Specifications will often aim to deploy solar photovoltaics (PV) to supply electricity for space heating and hot water. When retrofitting gas-based hot water systems this is a less efficient route since PV will always offset grid electricity at 136g/KWh, equivalent to 18 kg of CO2/m²/annum. Compare this to solar thermal which offsets gas emissions at 233g/kWh, or 148 kg of CO2/m²/annum. This makes solar thermal eight times more effective per m² than PV when addressing carbon emissions from water heating, translating to a smaller panel area for solar thermal on the rooftop. 

Resurrecting Solar Thermal 

With new high-efficiency, robust flat plate collectors and protective drainback, cylinders and controls to integrate solar thermal with electric top-up there is a real opportunity to resurrect systems which have fallen into disrepair. Most refurbishments where overheating has been the cause of shutdown will require new collector panels and pipework which fortunately is a relatively straightforward replacement as the re-installation process will have minimal impact on extant plant room appliances. This allows for upgrading existing gas water heating, saving energy, and reducing emissions from the existing system.

Alternatively, Adveco can support the transition to full electric water heating with solar thermal through bespoke system design and product supply. For smaller systems and schools with lower capacity demands, Adveco FUSION offers a pre-defined low-carbon system that is compact, easy to install, resilient and cost-effective. For organisations which are considering but not ready to commit to a heat pump-based system, FUSION T is available now with an option that delivers a twin-coil stainless steel tank and mounted ARDENT electric boiler and controls without the heat pump preheat. This iteration allows for solar thermal to be introduced into the lower coil as the system preheat with a small amendment to the controls to optimise top-up heating from the boiler as the pre-heat fluctuates across the year.

With FUSION now supporting capacities up to 750 litres with 24 kW heat output, it is suitable for solar systems designed for small to medium-sized buildings. While most solar thermal systems would be designed to split the preheater and after heater, this single-cylinder FUSION scenario avoids the typical requirements of a 50/50 capacity split between preheat and top-up. Adveco’s smart controls allow the system to ‘cheat’ in favour of the solar thermal delivering a 600-litre solar capacity in a 750-litre tank for an extremely compact option for an all-electric low-carbon emission solar water heating system with a minimal rooftop or façade footprint.

www.adveco.co

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Solar Thermal – Reducing Energy Demands To Cut Carbon & Costs

Capable of offsetting typically around 30% of the energy demands for water heating, solar thermal systems are ideal for schools and colleges that rely on large amounts of domestic hot water (DHW).

For the existing education buildings, 80% of which are still expected to be in use by 2050, the application of solar thermal pre-heat is a well-established means of reducing demands on prevalent gas-fired water heating helping to offset operational costs and actively cut carbon emissions. New build or refurbishment projects, however, are now more likely to be mandated to adopt direct electric but are finding that the move comes with a new financial burden as electricity remains substantially more expensive to operate than gas – currently by a factor of 3.8. Undisputed carbon and cost savings means we are seeing a definite upswing in interest for new solar thermal systems where a ten-year return on investment is very achievable.

A correctly designed and sized system will consider the daily usage and peak demands. Its aim is to serve all peaks from storage, with the size of the peak determining the size of pre-heat. The recovery time for peaks is what ultimately determines number of solar collectors a building requires. The design process also sizes usage with available space. A south-facing and unobstructed roof with an inclination of 30° from the horizontal is optimal, though by no means essential as modern solar collectors can be installed in a variety of permutations. Unsurprisingly, solar thermal collectors do suffer if the building is significantly shaded, in which case a commercial air source heat pump may be a preferred option to produce low carbon heat.

Modular, high-performance flat plate collectors can be situated on, or integrated into flat or sloped roofs, as well as mounted on a building’s façade. By far the most efficient way to heat water with solar energy, flat plate collectors offer a smaller footprint compared to equivalent solar photovoltaics (PV) for DHW. A typical 4 kW PV system requires approximately 16 panels covering 25m² of roof to match just three flat plate collectors covering just 6.6m² roof area. This makes solar thermal a prime choice when roof or facade space is limited.

 

Adveco collectors feature a copper meander absorber through which passes the solar fluid (glycol). The fluid transfers solar energy as heat to the system’s water via an indirect cylinder. To correctly manage solar fluid, drain back technology should be applied to protect the collector system from overheating. This can ‘cook’ the fluid to a tar-like consistency causing permanent damage to the collectors. As the name implies the solar fluid drains from the collector to a reservoir when not in use. Flat plate collectors with an integrated drain back module offer a more cost-effective (as there is no requirement for large solar storage) and more efficient (as there is no call to dump unused heat) approach. The technology has proven itself in the field with fluid changes required perhaps once in eight years, rather than the expected three. For new build properties with electrical connection, the gas-heater is replaced with an electric boiler and cylinder to supply the afterheat which raises system temperatures to a necessary 60°C. This hybrid approach maximises the solar thermal input, typically offsetting 30% of the electrical demand, although it could be more depending on location. Adveco has simplified this hybrid approach by integrating a packaged FUSION E electric water heating system to supply the after heat. This also gives the option of adding an electric immersion to the system as a backup for enhanced resiliency when assured water heating is deemed a critical service. The all-electric solar thermal approach further reduces carbon associated with grid electric systems and aids in lowering operating costs.

 

This hybrid approach can be further extended with the inclusion of air source heat pumps to provide the initial pre-heat for the system. Operating at lower temperatures with the cold feed maximises the efficiency of the heat pump, reducing electrical operating costs and raising working flows temperatures from 10°C to 40°C. This is not hot enough for commercial applications, so the pre-heated water is then passed to the mid-solar thermal system. Essentially free to operate, the solar thermal system boosts the working flow temperatures from 40°C to at least 50°C. Although not operating at maximum potential, there is enough advantage gained from the solar thermal to warrant the additional system complexity and capital investment. During summer months it is possible for the solar thermal system to deliver the necessary 60°C working flow for safe provision of commercial hot water. But to ensure safe, consistent, and necessary high operational temperatures, the water is passed to the FUSION electric water heater. Here final consistent water temperatures of up to 65°C are assured year-round.

To date, Adveco has designed and supports more than 800 live solar thermal systems, many of which are located on school, college and university buildings across the UK. The outlined hybrid approaches are unavoidable if the education sector is to seek a sensible, practical, and cost-effective path to low-carbon hot water as part of wider net zero strategies.

CLICK HERE FOR THE ADVECO WEBSITE

 

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Building Sustainability in Schools

Constantly challenging performance, the Department for Education (DfE) is expected to increase the focus on property-related efficiency, especially in terms of delivering sustainability across the estate. But understanding how a school property’s assets contribute to that overall performance, and how individual assets perform against technical criteria for sustainability has never been more challenging.
The complex technical issues that surround commercial grade domestic hot water (DHW) and heating applications within schools demands strategic, real-world understanding. Not only are there physical limitations when it comes to technologies on offer, there are considerable variances in capital expense and ongoing operational costs that without doubt contribute considerably to the annual costs of running a school.

The challenge of meeting sustainability goals
For education sites which typically exhibit a large DHW load, there remains a strong argument for employing gas-fired water heating. And, just as electricity is becoming greener, so too can the gaseous fuels when blended with hydrogen and other synthetic fuels. With publicly funded organisations increasingly being mandated to demonstrate clear and real investment in sustainable and low carbon technology schools face a complex, real-world and political challenge.
Far too often, school hot water systems suffer from poor application design where a lack of understanding of different types of hot water system leaves systems oversized to prevent perceived hot water problems. Inefficient and less environmentally friendly, such systems will prove more costly to build and operate for their entire lifespan. This can be further exacerbated by the introduction of Air Source Heat Pumps (ASHP) and Solar Thermal systems.


With ASHPs offering greater efficiencies in low-temperature systems, the high-temperature demands of domestic hot water (DHW) for school applications can be a challenge. It is recommended to calculate emissions at a working water temperature from the ASHP of 55°C, this is then hot enough to provide realistic levels of preheat for a commercial DHW system. Schools’ applications using heat pumps are going to be complex and, when compared to gas-fired alternatives, are going to have higher up-front costs. Offsetting this additional capital investment though are new efficiencies and sustainability that reduce CO2 emissions.
Now is also a good time to reconsider the integration of a solar thermal system as part of the premises. Not only a proven and extremely reliable technology, for the past 15 years solar thermal has offered a clear path to reducing CO2 emissions for schools that rely on large amounts of hot water.
Solar Thermal provides an effective way to offset the new financial burden that comes from moving from cheap gas to currently far more expensive electricity. A ten-year return on investment becomes very achievable, and, with zero emissions, the undisputed carbon and cost savings make this technology increasingly more viable.
Solar has always been used as a preheat with coldest water possible to maximise the efficiency and output: this gives maximum free heat with no carbon emissions. But there is a good case now for using solar thermal with heat pumps and electric if set up as a mid-heating system which can lower both carbon and cost.
None of the above are a single, all-encompassing answer for schools seeking to achieve Net Zero, but when used together they can provide estates managers with reliable, business critical hot water and heating systems that deliver value for capital investment, exhibit lower ownership costs over their lifetime and will help to meet current sustainability targets. They also provide a clear path for integration of new technologies, such as high temperature heat pumps and hydrogen ready appliances which will ultimately help to deliver Net Zero by 2050.

At Adveco, our dedicated application design team provide accurate, bespoke sizing, for both new build and refurbishment projects. Once correctly sized, we can recommend, supply, commission, and service the optimal appliances whether they be gas, electric or a mixed hybrid approach that incorporates solar thermal, heat pumps and heat recovery systems. This is the best way of ensuring schools hot water demands are met in the most cost-effective and sustainable manner.

www.adveco.co/sectors/education

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The Active – Office of the future

The UK’s first energy positive office, the Active Office, was opened in June last year at Swansea University. Designed by SPECIFIC Innovation and Knowledge Centre to be powered entirely by solar energy, the Active Office aims to generate more energy than it consumes over the course of a year.

The Active Office isn’t just meant to be a high performance building for its own sake, but also to demonstrate how well buildings can perform with technology available today. The building is packed full of cutting edge, commercially available technology to help generate, store and manage energy for the building.

One piece of technology provides both electricity and heat to the building; the photovoltaic thermal (PV-T) system by Naked Energy. Made up of a number of photovoltaic panels contained in vacuum sealed tubes, the system has been mounted onto the front elevation of the building and could potentially provide heat energy for the entire building through spring, summer and autumn.

More solar energy is collected through the roof which is covered in, or more accurately made up of, solar cells. The PV cells are bonded directly onto pre-painted steel to create a roofing system that can be installed using conventional methods. The Active Office features the first commercial installation of BIPVco’s technology on a curved profile, which aside from adding architectural flair, will also generate power throughout the year even in low light conditions.

The various systems are monitored by extensive metering installed throughout the building, enabling SPECIFIC to determine where energy is being generated and consumed. This is reflected in a real time display in the entrance foyer, allowing occupants and visitors to find out how the building is performing.

However, the building can’t reach its energy positive target if all the energy it generates is wasted. “We took a fabric-first approach to reducing energy consumption,” commented Joanna Clark, Building Integration Manager with SPECIFIC and Architect for the Active Office. 

The Active Office was designed and conceived by SPECIFIC Innovation and Knowledge Centre and funded by Innovate UK with support from Swansea University and the European Regional Development Fund through the Welsh Government.

It was manufactured offsite by Wernick Buildings, in their factory in nearby Port Talbot. SPECIFIC knew that modular construction could deliver the levels of performance they needed against a challenging programme and budget.

Months later, the choice of modular is being borne out by data. On current performance, SPECIFIC predict an annual consumption of approximately 20MWh versus an annual generation of 24MWh.

The future looks bright for this new type of solar-powered building design. In September, the Chancellor of the Exchequer Philip Hammond announced funding for the Active Building Centre through the Industrial Strategy Challenge Fund and UKRI. The new independent national centre will seek to remove barriers and accelerate market adoption of new Active Buildings. 

It seems likely that modular construction will play an important part in progress towards a low carbon future. 

For more information:

www.wernick.co.uk | www.specific.eu.com

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