What Should Come First, Solar PV or Replacing Transformers?

Comparing solar Photovoltaic systems to distribution transformers is not exactly straightforward, the former is used for generating electricity and the latter for transmitting and distributing it. Does that make it a case of apples and oranges comparison then? Not quite.

The shift to renewable energy surged exponentially after the prices per kWh have come down. Governments and big corporations realised that diversifying the energy mix and including renewable generation is not only good for the environment but also for energy security.

In the past 12 months, almost half of the electricity generated in the UK was low carbon. 4% of which was generated by solar PV, making it the seventh biggest electricity source in the country. The government has invested a lot in solar PV, from funds and incentives to legislations that allow users to export electricity to the grid through feed-in tariff previously and smart export guarantee now.

Transformers, on the other hand, have not received any support from the government. No one wants to talk about grey boxes that get put away with "Danger, High Voltage" sign and end up being forgotten for decades regardless of how much energy they waste or carbon emissions they result in emitting. I realise they are not as attractive as other emerging technologies, but they offer a huge potential for energy savings that have been overlooked for years.

I argue that comparing apples to oranges is doable, taking into consideration calories, weight, price and nutritious value. Similarly, comparing solar PV to transformers is valid taking in mind the Net Zero targets and the very little we can do with the allocated resources and the technical limitations. Everyone knows that as a rule of thumb in energy, efficiency comes before generation just like reducing comes before recycling in the 3Rs. After all, what is the use of generating green electricity if it is going to waste?

Why Transformers?

The main function of distribution transformers is to convert the electrical current from one voltage to another. Transformers waste energy as a by-product of their operation. The wasted energy happens on two forms; load losses and no-load (core) losses.

Transformers are responsible for 25% of the UK’s network losses. The EU estimates that 2.9% of all electricity generated across the continent gets wasted through transformer losses, according to 2008 across the EU27. That amounts to 93.4TWh which is enough to power Denmark for 3 years.

When the conversation about energy efficiency takes place, people immediately start thinking of ways to save energy inside the building (lighting, double glazed windows, inverter air conditioning units, etc.) but very little think of transformers. Transformer losses, despite being undesirable, they are unavoidable. But Wilson Power Solutions spotted a great energy efficiency opportunity in reducing these losses.

How to Make Transformers More Efficient?

Core losses occur 24/7 from the moment of energising the machine, the only thing we could do about it is changing the core metal material from Cold Rolled Grain Oriented (CRGO) steel to amorphous metal and increasing the winding.

The cores of conventional transformers consist of stacks of laminations that are made from silicon steel with an almost uniform crystalline structure (CRGO). In transformers with amorphous cores, a ribbon of steel is wound to form the core. The big benefit of amorphous transformers is that amorphous steel has lower hysteresis losses. Simply put, this means that less energy is wasted as heat during the magnetisation and de-magnetisation of the core.

Amorphous metals are made of alloys that have no atomic order. They are made by the rapid cooling of molten metals that prevents crystallisation and leaves a vitrified structure in the form of thin strips. Due to the random molecular structure, this type of metal has also been given the name "The Metallic Glasses".

Eco Design Directives

The European Commission issued regulation No 548/2014 on implementing Directive 2009/125/EC regarding small, medium and large power transformers. The regulations are referred to as Eco Design Directives for Transformer Losses Tier 1 and Tier 2. Tier 1 was effective as of the 1st of July 2015 and Tier 2 will come into force on the 1st of July 2021 (less than two years from now).

Tier 1 and Tier 2 regulate transformer losses by forcing most new built transformers to have improved (lower) losses. I believe these targets could be pushed even more.

Solar PV or Transformers?

Through the Freedom of Information (FOI), we made a request to Ofgem enquiring about the average age of transformers in the UK. The response was surprising that the average is 64 years. There are transformers that were installed pre-1950 and are still up and running but unnoticeably, are silent energy guzzlers.

The ideal age of a transformer should be around 30 years. Most transformers are designed for 25 years of operation. Replacing old inefficient transformers with new Eco Design compliant ones makes perfect financial and environmental sense.

I believe organisations should invest in both solar PV and transformer replacement when they can. The only problem with that is when budgets are tight or there is no space to install solar panels. But if it is a question of which, transformer replacement makes more sense.

Taking a case of replacing an average 1000 kVA transformer installed in the 1990s with an Ultra-Low Loss amorphous one could save an organisation over 32GWh of electricity every year. This helps organisations avoid more than 9 tons of CO2 emissions annually. Over its lifetime, the new transformer would have saved the owner over ￡120,000 after paying back the initial investment just through improved losses.

Carbon wise, replacing an old 1990s transformer with an Ultra-low loss one is equivalent to generating energy from 100 solar panels (instead of fossil fuel) and is 60% cheaper. Now if the transformer was installed before 1990s, then the savings potential figures could be bigger. And this is a low hanging fruit for reaching Net Zero!

So in the “apples versus oranges” situation, energy efficiency should come first, thus, an organisation should ensure to have the least energy wastage in place before thinking of generating electricity. Because realistically speaking, unfortunately, resources are limited when setting sustainability or carbon reduction policies and if it was a choice of which technology to invest in first, transformers make more sense thinking carbon and ￡ per kWh. But again, I recommend both when possible and it goes without saying that this comparison is applicable to the UK with the up-to-date data and with the case of having an HV network to start with!