LaZer2 solar thermal
Our LaZer2 solar thermal system can be mounted in many
ways. The design makes them very versatile and the system
sizing can be increased by adding multiples of panel units.
Flat roof systems
There are two options available when planning to install
our solar thermal system to a flat roof. Either fix them to the
construction in some way, or use an arrangement of carefully calculated ballast, positioned to resist the wind loading conditions in the installation location. Solar UK have extensive experience providing solutions that work well in both situations. The loading of a structure and the feasibility of achieving a suitable fixing are the main considerations when deciding which option is most suitable for the project in hand.
The LaZer2 has an internal manifold, developed to maximise efficiency when extracting energy with minimum amount of losses. It incorporates a direct series manifold arrangement whereby each panel, comprising of nine vacuum collector tubes, designed so that the heat transfer fluid passes through the length of each collector tube twice, and all nine tubes in turn, before it joins the flow pipe. This enables a more efficient and enhanced temperature change in each circulation of the system. This also increases turbulence and surface area the fluid comes into contact with, within the systems` manifold, and so enhances the efficiency of temperature exchange between the conducting profile, manifold U-tube and heat transfer fluid.
This design is unique to Solar UK`s LaZer2 solar thermal panel, enabling the system to focus the energy towards the desired heat destination, and reduce the retention of usable energy in the panel, making LaZer2 more thermally responsive.
LaZer2 can be utilised in many ways. Typically, it is used to indirectly heat a stored water volume in a vessel via an internal coil, or it is used to heat the secondary water volume via a heat exchanger. In some instances, it is used to heat a heat storage medium/volume which in turn has further exchanges to either heat exchangers or extraction coils. Phase heating of different volumes of water is also possible depending on the application priorities and this is often referred to as pre-heating or buffering.
A typical solar hot water heating system consists of an indirect
hot water cylinder, with internal heat exchange coils fitted for
each of the heating circuits, as can be seen in this diagram.
(click to enlarge)
Another option is to have a pre-heating/pre-feeding arrangement,
where two vessels are installed in tandem. In this arrangement the
flow of water passes through both cylinders, with heat input occurring in
each, in turn, before going to the outlets (taps/showers). An example of
how this can be achieved is shown here.
(click to enlarge)
Heating a swimming pool with the LaZer2 solar thermal system offers huge savings on energy costs compared with conventional fuels. So our solar thermal systems can achieve very short payback periods. The typically seasonal use of swimming pools makes pool heating a very suitable application for this technology. A layout showing the pool pumping and filtration equipment required for all swimming pools, coupled with an inline solar heat exchanger and a conventional inline boiler heat exchanger can be seen here.
The setting on the boiler system in this example would ensure the desired comfort level is reached whenever the owner/user wishes to take a swim. The LaZer2 solar thermal system is able to utilise all available solar yield to heat the pool water and satisfy the boiler temperature control thermostat. This set up allows the heat input from the sun to be used to off-load the work otherwise done by the boiler, and to prevent additional heat from the boiler from being required for the majority of the time.
The LaZer2 solar thermal system is versatile and can be used for all sorts of purposes. Heat stored for other purposes is common and bespoke service systems can be designed to lower running costs and offset CO² for many different client demands and objectives (Heat).
Although some clients wish to use solar thermal technology to provide space heating, this application is not well suited to the characteristics of solar thermal technology. This is partly due to the nature of solar gains being most abundant during the low demand periods for space heating. The ability to achieve some benefit by contribution towards space heating is easily achievable, however as a viable space heating energy source any solar thermal system would have to be dramatically over sized to satisfy demand during the coldest and darkest winter months, and would therefore be in a constant state of over production during the bright summer months.
Where a logical sizing justification exists, it may then, in addition
create opportunity to utilise the energy available in alternative
but similarly effective ways. For example, Solar UK often
encourage our clients to incorporate the capacity to heat
domestic hot water when designing a system for heating a
swimming pool, as this is a very sensible additional utilisation for
the energy that will be available from the solar system.
Typically we look to allocate between 55-85 litres of
dedicated stored water to be heated by each m² of the
LaZer2 solar thermal panel aperture, each day in an indirect
hot water cylinder. This ratio is capable of producing
between 55-85% of the HW demand anticipated
in a domestic dwelling, depending on the inhabitant’s
usage patterns. Although variations in usage and
weather conditions will account for variations in system
performance, the LaZer2 solar thermal system
is capable of making the most effective use of the
solar energy available at any given time.
It is important to appreciate the capabilities, and limitations of a well designed solar thermal system. Due to our modern expectations and the level of comfort we have become used too, the majority of solar thermal systems are connected to heat water with all available solar energy, whilst a secondary energy source is incorporated to ensure the desired temperature and recovery periods we have become used too are maintained. Solar thermal systems are designed to be super efficient, whilst traditional heat sources generally prioritise effectiveness over efficiency. As these traditional water heating systems are capable of heating water in a very short period of time and on demand, the heating characteristics of a well designed solar system is sometimes miss perceived as ineffective, immediately following a peak demand period or over night when solar gain is not available. Many traditional water heating systems have raised expectations by the almost instant release of energy from primarily nuclear power or fossil fuels allowing water to be heated instantly on demand. Quality solar thermal systems take into to account the duration of light energy available and the demand for hot water throughout the year and so are sized to achieve the desired quantity of water heating with the minimal of equipment outlay. Should an increase or decrease in the hot water demand occur the perceived effectiveness of the solar system can often be affected.
Depending on the priorities set by the client, and using the LaZer2 system, we can tailor a system to best suit needs of the buildings end users. Also by working closely with mechanical and electrical consultants we regularly find the right balance between ensuring a building service provision is achieved with the minimal use of conventional fuel sources, thus maximising the utility of free, environmentally friendly solar energy.
The wide range of conditions presented by the projects encountered can be reduced to several types of mounting system by familiar characteristics and the sub-sections contained by them. These are detailed in the next section.
Pitched roofs require pitched roof fixings. Here is a sample of the typical pitched roof fixings available for the LaZer2 solar thermal panel.
- Truss Straps for tiles
- Wood to metal dowels
- Seam Clamps for seam roofs
- Top hat profile for composite sheet roofs
Due to the vast diversity of pitched roofing materials and systems we employ various methods of securing equipment in place. It is of course paramount that we transfer loads safely to the structure without compromising the integrity of the construction envelope. This is why we invariably attempt to pass through the title courses, fixing directly to the load bearing structure without impeding the tiles function. Due to the wide range of tile types that we encounter, we have several profiles of fixing brackets in our arsenal. Typically they will be made from either; stainless steel, or aluminium, this is for strength and longevity and in each case will be tested to be fit for purpose. Due to the nature of certain roof coverings, it is necessary in some instances to penetrate roofing materials. This can be done carefully following our tried and tested methods to ensure the resulting integration of materials, continues to perform as well as it did prior to the penetration being undertaken. All our workmanship is covered by our labour warranty (*see warranty section for details).
wind to pass between them, however it can be an issue for close consideration, particularly if being implemented on a retrofit/refurbishment of an existing building, or applying this technology to a building in the late stages of design/construction.
Fixed flat roof arrays require physical connection to the building by high tensile bolts or other positive secured fixing. Examples are shown here in this montage of previously completed installations.
Ballasted arrays are popular because they don’t require any fixings to be passed through the finished roof materials. Providing the structure and roof covering material is suitable, this tends to be the favoured method of ensuring collectors can resist wind loading and so remain in the position intended. It is common to use sacrificial layers of material to separate the ballast blocks from the roof coverings, in order to avoid wear and tear otherwise caused through different rates of thermal expansion.
Ground mounting options include ballast but more commonly incorporate ground mounting posts which are driven into the ground like piles. The benefits of this system are that it can be used on land with no permanent environmental effects. Options extras include a terram and shingle covered area below the panels to ensure low maintenance by removing the need to trim weeds and grasses under and around the ground mounted panel arrays.
We have extensive experience with various building types, materials and fixing systems. We are able to engineer bespoke options for unique projects as well as share the benefit of this experience with any designers or specifies at the earliest stages of a new project or retrofit. We are also keen to keep our eyes open to new and improved technology, and so will often work closely with designers and roofing specialists to make sure where possible that we use brand compatible materials and systems to maintain existing warrantees and ensure compatibility. We can provide structural loading calculations if the client is not in a position to undertake these checks. We are insured to carry out design work, however are happy to provide product specific design input and support to an overall building/project design, as this can sometimes be the most cost effective option for our client/clients representative, depending on the structure of the project/contract. LaZer2 collectors can be hung vertically from a wall or laid flat with a lower reduction in performance than would result from doing this with alternative designs of collector. For more details please contact our offices and ask to speak to a technical advisor.
– Independent testing by SPF Institut FÜr Solarechnik verifies the LaZer2 product to be in the top six, highest performing, commercially available collectors in the market place, and, until recent years it has been the highest performing vacuum tube collector of its kind.
As with all projects, success often relies on the priorities of the intended design being clearly defined so these can be married with the operational characteristics of solar thermal technology, to achieve the best performance from the resulting integration of systems.
Factors that often influence the sizing of a system, which are often divisive to the performance targets of a text book system include; space limitations of plant areas, planning and building regulations targets which stipulate a percentage/quantity of energy to be achieved from renewable sources, and the peak demand and recovery target rates required of conventional fossil fuel fired systems which can remain un exercised compared with the sporadic solar yield characteristics which can reach and exceed their design capabilities on a regular basis in correlation with the weather conditions.
A typical LaZer2 system is capable of producing somewhere between 65-95% of the energy required for heating hot water in domestic buildings and achieve a payback period through energy savings alone of between 7-10 years. With a design life which well exceeds 25 years, this makes for a very viable addition to any building regardless of additional; moral, environmental and financial motives which may effect someone’s discussion. Some customers who are more aware of the system characteristics and can be more flexible with their water usage patterns are able to avoid using any other heat source for the majority of the year. In buildings where the demand requirements are prioritised over the availability of free renewable energy, such as hospitals and commercial food preparation facilities, it is common that the supply of hot water on demand is ensured by conventional means whilst the solar is set up as a supplementary system to offset the maximum amount of fuel it can for the initial investment.
The first item to tackle when sizing a system for domestic premises is what the stored hot water volume should be. This will typically be 180ltrs<250ltrs in most 2-4 bed homes in the UK. It would be recommended that any replacement cylinder be sized in accordance with this convention. For this size range of hot water system it would be recommended that 2<3 LaZer2 collectors be installed to heat the stored volume via an internal lower coil and the conventional heat source (boiler) be connected to provide supplementary/backup heating via a second internal upper coil. This format is most appropriate for homes and assumes that the cylinder volume will be draw off and refilled for the most part on a daily basis. This approach can be scaled up for larger buildings such as university halls of residence, hotels or apartment blocks with centralised plant, as the typical volumes and usable patterns are comparable with self contained domestic properties.
In offices and educational buildings, the use of hot water is likely to be slightly different and for the most part will be during normal working hours. The volumes used for cleaning and in catering facilities will become the peak demands and had washing facilities will make up the remaining demands. The size of the solar system will revolve around the realistic daily quantity of hot water used by the building, and the number of collectors will be chosen in order that this volume is heated to the desired temperature on a daily basis for the majority of the year.
Because the design of the LaZer2 collector is such that the variation in performance throughout the year is due to the number of daylight hours and the clarity of light available, there are inevitably differences between the winter months and the rest of the year. The sizing of the system must take into account this and accept that in the winter months there may be a need to supplement solar heat with a conventional heat source, and in the summer the yield may exceed the demand on occasion. It is important to get the balance right so as to provide as much of the hot water possible without losing efficiency through the system preventing the use of available solar energy because the stored hot water is too hot to apply further heating to it.
There is a balance between efficiency and effectiveness that needs to be evaluated and targeted when considering the number of panels and volume of water to be heated.
Effectiveness = the volume of water achieving or exceeding the desired minimum temperature in line with the demands of the occupants of the building.
Efficiency = putting to best effect, all the energy available from the sun in order to offset the maximum amount of energy otherwise obtained from conventional fuel sources, for the minimum of equipment cost.
Where the balance between the number of collectors (which equate to approx 1m² each) and the stored water volume falls below 65ltrs/m² there is a likelihood of an unusable surplus of solar energy, produced from the equipment during the summer months. This problem can be overcome if the design takes into account that the volume used each day is greater than 65ltrs/day resulting in a larger volume to be heated by solar each day. On the other hand if the stored volume exceeds 85ltrs/day/m² of collector, then the system is less likely to achieve the required usable temperature other than in idyllic conditions during the summer months.
In buildings where the temperature of a volume of water is required to be constant for the hot water system to work effectively, such as in some systems which incorporate heat stores or where legionella threats are considered very high. It is not very effective to incorporate solar thermal technology without having a rethink of the existing system design. This is because the capacity for solar to add heat to water is not available if the water is already at the maximum safe temperature allowed by the system. The efficiency of the solar system is enhanced by a daily draw off and replacement of the cylinder volume with cooler water. In hospitals and other types of public service buildings which have this scenario, the LaZer2 system can be configured to pre-heat water which enters the primary calorifier, allowing the primary calorifier and secondary return circuits to operate at higher temperatures between peak demand periods. Due to the slower recovery rate of solar compared with other heat sources, and the lower differential temperature between the primary and secondary sides of the solar heat input exchanger, stratification is often utilised to allow the hottest water to be available to the outlets whilst the coolest water to be introduced and remain near the heat input location for longer. Many industrial or commercial hot water systems incorporate de-stratification in order to enhance the volume of water available for use and the reduce the potential for bacterial hazards. The LaZer2 system can be configured to achieve these priorities whilst also enabling the solar to work effectively providing some basic changes are made to the conventional hot water systems operation philosophy, and the volumetric demands of the property are attainable within the confines of the plant location.
When designing a system for heating a swimming pool it is again important to consider the intended result related to the achievable performance of different sizes of system. Here in the UK, for a typical below ground swimming pool of modern construction, average depth 1.5m, 30% of the pool surface area would be sufficient to provide a suitable level of heat input to reach desirable temperatures (26<30ᵒC)for what is considered to be the average British swimming season (May to September). For pools with no other heat source, or pools with constructed such that greater than average temperature losses will be experienced, it is recommended that the percentage be increased to 50% or the surface area. Indoor pools which are well insulated (modern) it can be sufficient to reduce the area of solar collectors to as low as 15<25% of the surface area. Often budget will affect the size of system chosen, but heating swimming pools can often be the most efficient use of solar thermal technology due to the relatively large losses and large volume of water they contain.