Solar Panel Systems

There are two main types of solar panel systems:

Solar photovoltaic (solar PV) – these panels convert the energy in sunlight into electricity for use in the home.

Solar thermal – these panels use energy from the ambient temperature and sunlight to heat water.  They require a hot water tank. A water/gycol mixture circulates through the panels, which gets heated by the sun’s energy which then passes though through coils in the hot water tank to heat the water in tank. It can also be used in wet underfloor heating systems.  

Both systems have a place in residents’ homes. This article covers some basics of these systems: how they work; how they can benefit people living in their homes; and behaviour changes needed to  maximise their effectiveness.

Basics of solar panels

Installation

For both systems the panels can be mounted on the roofs of homes, outbuildings, parking canopies or on ground mounted frames. They should ideally be facing south and at an angle between 30 and 40 degrees. It is important to note that the further from south the panels face, the less energy they can convert into electricity and hot water. East and west facing solar panels can still be usefully productive, but north facing panels may not justify the initial cost.

Sunlight dependency

Although the systems can work when not in direct sunlight, they do need some light to work. This means that the length of time the panels are functioning varies from summer to winter, according to sunrise and sunset times. The graph below shows an example of the electricity created by solar PV across the year.

Source: RISE

Alongside the length of sunlight time, the strength of sunlight is also important.  Lower winter strength reduces the amount of energy the solar panels can create. The next graph shows an example of the potential electricity created by a single solar PV system during the day, and the difference in energy creation between summer and winter. Solar thermal systems are affected by the sun’s strength in the same way.

Source: RISE

It is important to recognize and brief residents on the differences in energy creation across the year and each day. By understanding this and judging the impact on their energy use on an annual rather than weekly basis, they will see the benefits of the systems. This should also reduce calls from residents about the systems not working in the depths of winter!

Using the systems

Finite Resource

The energy created by solar systems is finite, once the sun sets energy production stops. For solar thermal, hot water is available until the tank of hot water runs out or cools down. For solar PV, electricity will stop being generated / useable immediately.

Behaviour changes and benefits

Residents need to adjust their habits to make the most of the generated energy.

For example, if a resident with solar thermal has a bath that uses all the hot water once the sun has set, they would have to use an immersion heater to re-heat the water in their tank. Whereas if they had the bath in the morning, the tank would reheat during the day to be ready in the evening for washing up.  

With solar PV, the resident could use the timer delay on their washing machine. This would ensure that the appliance was used when the sun was at its highest and the solar panels were creating as much energy as possible. It would not only reduce or remove the need to buy energy from the grid for that task later on, but it would also use up the electricity while possible.

Using electricity as it’s created is much more cost effective than selling the excess electricity to energy suppliers through the Smart Export Guarantee (SEG). The rate that energy suppliers will buy energy from homes is much lower than the rate you buy electricity from that same energy supplier. So, if you can use as much energy as possible from your solar PV system, it will reduce the energy bills you have each month.

Behaviour change

The benefits of Solar PV varies depending on the residents in the home. For a family where the parents work and the children are in school during the day, the benefits are much less than for those at home all day. As the section above showed, energy use for this kind of family peaks when the energy creation is dropping. All the energy being created in the day doesn’t benefit the family unless they change some of their behaviours (e.g., use timer delays on washing machines) or fit battery storage.

A retired couple living in the same home, who are at home during the day would benefit far more from the solar panels. This is because they can use it instantly and are therefore access the free power as it is available during the day.

As we have shown, the amount of electricity created in the winter vs the summer is different. If you have a home heated by electrical heaters, you will only make a small difference to the energy consumption through solar panels. As the panels will make little difference in the winter, when you need the heating.

Battery Storage

Batteries store unused electricity created by the solar PV panels during the day, to be used later. This can then be used when the energy use is more than the energy being created by the panels.

• Red hatching indicates where energy use is higher than that being created or stored in the battery. This means the household is using the grid for its energy use
• Yellow hatching indicates when energy use is higher than creation, so the battery is used to provide the home with energ
• Green hatching indicates where the energy used is less than (and so is fully supplied by) that being created. At these times, the battery is also charged

For the family that is out at work during the day, the fitting of a battery can capture the energy being created during the day and help reduce energy from the grid. This will reduce their energy bills.

For the resident that is at home all day using energy as they need it, unless it’s a large solar array providing a lot of power, they may not benefit in the same way from the battery storage.

Power Cuts

In the situation of a power cut, most solar PV systems will stop working. This is to remove the risk of any electricity being exported to the grid from the home when there may be staff working on the cause of the power cut. Solar PV’s can be set up to be able to continue to provide power during a power cut, and for some residents this may be valuable to the resident. For example, if they have need for powered medical equipment.

Like solar panels, the battery storage needs a power source to continue to work. As with the panels, this can be set up to continue to operate in the case of a power cut. This needs to be specified at design. For residents with Air Source Heat Pumps this can provide the power required to maintain heating for a period of time.

Solar Diverters

An alterative to installing a battery for using excess energy is to have a solar diverter. This uses any excess energy to do another task in the home. This is often to heat water in the hot water tank, where solar thermal isn’t fitted. As the amount of energy being created exceeds the energy use requirements it kicks in the immersion heater in the hot water tank, heating the water during the day. This will reduce the residents’ bills through a reduction in energy use heating their water.

 Fitting

MCS Standards

Although not mandatory (unless specified for funding), it is best practice to ensure solar systems are fitted to MCS standards and receive MCS accreditation. This ensures the system is installed by qualified and experienced fitters and provides the necessary certification for energy suppliers (Smart Export Guarantee) and funded works such as meeting Trustmark lodgments.

Design Considerations

Effective and safe design takes into account the roof space available, orientation and wind rating. It can help residents understand the benefits they can expect to gain from the solar.

The solar PV panels can be fitted on top of current roof tiles, or can be fitted in an inlaid fashion, where they don’t stand proud of the roof. Decisions on these options can be driven by the lifespan of the current roof, planning requirements or other needs.

Source: Marley

When fitting solar panels, you need to inform the Distribution Network Organisation (DNO) and your local planning authority. The DNO owns and manages the energy infrastructure and needs to be aware of new solar PV systems. There may be planning restrictions locally that can mean limitations around both systems. Bird caging and fire risk assessments are other areas to be aware of. All four of these topics (the DNO, planning, bird caging and risk assessments) are dealt with in more depth in the RISE quick guides (forthcoming in November). 

Conclusion

Solar PV and Solar thermal are both great options to support residents in reducing their energy consumption, lowering their fuel bills, and helping reduce the risk of fuel poverty.

For this to come to fruition, landlords need to carefully consider the needs of the household when they specify and fit the solar systems. This should support the residents in that home, and how and when that resident uses energy. Whether this is fitting battery storage, solar diverters or purely a simpler solar PV system all relies on the needs of the household and the support you want to offer.

For more specific information on the different topics raised here, have a look at the specific toolkits and quick guides that will give you more information on that subject.