Sunny Thoughts

Sunshine for the consumer


PV After the Feed in Tariff - FiT RIP!

The Feed in Tariff is due to close in April 2019, and currently the FiT payment is very small, so its significance in the decision to install a solar system is reducing, soon to become totally irrelevant. No longer will the purchaser be looking for a financial vehicle for money to give a return on investment, they will be looking for value for money, and an energy supply in return for their investment. The current payment for exporting energy is just over 5p/kWhr, so when you are buying energy for 18p/kWhr or more, it makes more sense to generate some of your own and to change usage patterns to use it at the time of generation, put the washing machine on, charge the electric car etc. To maximise use of your own energy even more you could fit an energy diverter to divert any energy export into heating water, or install a storage battery to store it during the day for overnight use.

System Design

The original design ideas developed following the introduction of the Feed in Tariff was to generate as much as possible over the year, this drove the ideal system design along the lines of a south facing roof at a pitch of 30º that maximised the total generation but gave a bell shaped generation curve peaking at 12 midday. This is likely, domestically, to be the time of least use, and commercially a low morning and evening generation is little use when consumption is steady all the working day. With this principle in mind we now need a re-appraisal of the design of the system. Now and in the future, it represents a better saving to have energy generated when you want it, so it could be better to look at other orientations and other angles dismissed under the “old thinking”.

Another design consideration with this installation is whilst it will be good for spring, summer and autumn, in the depths of winter the sun rises in the south east, is low in the sky at midday, and sets in the south west. Whilst the system will still generate with the sun at this low angle what ideally is needed for the winter months is some panels facing south and set at a steeper 50º pitch – although at this angle, in the height of the summer these will miss eight hours of early morning and late afternoon sunshine! Nothing is ever straight forward! As you see the design is a compromise trying to target your specific requirements.

Storage

If you have solar system that faces south a good energy saving move would be to add a diverter, or battery storage. The midday generation peak can then be stored and used later or overnight. The battery storage will then be empty again and ready to store the next days sun peak.

Adding storage can influence the solar system size. If a larger PV output is installed, good for additional energy anyway, the surplus energy will recharge the batteries. A bigger solar system is particularly beneficial on the shorter days in the winter.

What all this illustrates is the need to consider the energy requirements when designing a solar system. In a typical situation the roof might already exist, so there is little design flexibility but with the knowledge of the sunpath and the energy requirements, the most appropriate design can be arrived at, and the building owner can understand the issues and what compromises need to be considered. All buildings will benefit from solar energy, the system just needs to be designed to maximise the output at the times there is a demand, or stored until needed.

Looking into the future

Considering the bigger picture, the electricity supply network operators will have less problems with solar systems that are targeting the demand and giving a flatter generation profile daylight hours. They don’t want a large generation peak from every system in the district at midday! – which they then have to deal with. Storage will further help them by buffering both the generation peaks and the demand peaks.

Export Limitation

Another helpful technology is the development of export limitation. This means that given the roof space, a much larger system can be installed to meet the building demand but the maximum export to the grid can be limited to meet the requirements of the District Network Operator. This principle is helpful in a commercial situation to meet a working week day demand but still cope with a weekend shut down. Also, domestically a higher winter demand can be met but then still control the maximum export for the DNO requirement in the summer.

To sum up we will discuss with the building owner to establish what is required and then propose a system that best fits the site, the usage pattern, and the budget. Typical system sizes used to be up to 4kW peak but these days with the demise of the FiT payment typical domestic system sizes are 4 to 8kW peak, with export limitation if necessary to meet the Network Operators maximum allowance. The default permitted export limit is 3.68kW/phase and permission has to be obtained to exceed this. In most cases this is allowed, but if not export limitation is programmed in.

Another helpful technology is the development of export limitation. This means that given the roof space, a much larger system can be installed to meet the building demand but the maximum export to the grid can be limited to meet the requirements of the District Network Operator. This principle is helpful in a commercial situation to meet a working week day demand but still cope with a weekend shut down. Also, domestically a higher winter demand can be met but then still control the maximum export for the DNO requirement in the summer.

To sum up we will discuss with the building owner to establish what is required and then propose a system that best fits the site, the usage pattern, and the budget. Typical system sizes used to be up to 4kW peak but these days with the demise of the FiT payment typical domestic system sizes are 4 to 8kW peak, with export limitation if necessary to meet the Network Operators maximum allowance. The default permitted export limit is 3.68kW/phase and permission has to be obtained to exceed this. In most cases this is allowed, but if not export limitation is programmed in.

Sunshine for the consumer
Sunshine for the consumer
Sunshine for the consumer
Sunshine for the consumer

A Sunny Future for Business


Most businesses operate in the daytime so their energy consumption occurs at the same time as the solar energy generation, a perfect demand matching supply time, all we need to do now is the calculations to make the amounts add up.

As with domestic systems a bell curve with peak generation at midday from a south facing system is not as useful as a system facing east/west giving a much flatter generation curve. Take for instance a business working from 8.00am to 6.00pm, it makes no sense to have a south facing only system which gives a gradual energy increase peaking at midday, and tailing off in the afternoon.

What would be better commercially is to have a system with east and west facing panels at a low angle that will give generation earlier in the morning and later in the afternoon, and much flatter whole day generation profile. 

Financially there is nothing business hates more than unpredictability! Adding solar generation to the roof of the building reduces the outgoing cash flow and adds predictability to the future energy costs. Once the capital cost is covered the solar system will not only produce free energy for the business to use for probably in excess of 30 years, it will reduce the outgoing annual costs and insulate business cash flow from the vagaries of the energy market. 

From a publicity perspective it will also indicate significant business responsibility prestige with its visible environmental responsibility, CSR (Corporate Social Responsibility), and reducing carbon emissions.

A Sunny Future for Business
A Sunny Future for Business
A Sunny Future for Business
A Sunny Future for Business


A very appropriate quote from John Ruskin (1819-1900) on price and value ...little has changed in the principles of business over the last 120 years!

"There is hardly anything in the world that someone cannot make a little worse and sell a little cheaper, and the people who consider price alone are that person’s lawful prey.

It’s unwise to pay too much, but it’s worse to pay too little. When you pay too much, you lose a little money – that is all. When you pay too little, you sometimes lose everything, because the thing you bought was incapable of doing the thing it was bought to do.

The common law of business balance prohibits paying a little and getting a lot – it can’t be done. If you deal with the lowest bidder, it is well to add something for the risk you run, and if you do that you will have enough to pay for something better."

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