How we’re meeting the challenge of 100% renewable thermal energy

At Unilever, our Climate Transition Action Plan sets out the steps we’re taking to reach our climate targets, including reducing greenhouse gas emissions in our own operations by 100% by 2030, against a 2015 baseline.

In a series of interviews, we put the spotlight on some of the people who are helping to deliver our action plan and make change happen.

Vivek Nesarikar, our Global Engineering Manager for heating technologies is based in Mumbai, India, and has been with Unilever for 11 years. Here he explains how we’re using waste heat energy to help lower our operational emissions.

What does Unilever use thermal energy for?

As well as providing heat and hot water in our factories, thermal energy sources can be used during production processes, like pasteurisation for our ice cream, and for cleaning processing equipment in our machinery (known as CIP – Cleaning in Place).

In our operations, thermal energy use accounts for most of our carbon footprint. When we develop decarbonisation roadmaps for our sites, thermal electrification – either through heat pumps, electric boilers or a combination of both – is emerging as a common solution.

In total, over a third of our thermal energy use is currently drawn from renewable sources. To meet our target of achieving 100% renewable heat by 2030, we will be looking to significantly increase our use of heat pumps across our operations.

Biomass is energy created using material from forests or farming, biomethane is gas produced through the breakdown of agricultural residue or gases from landfill, and biodiesel is a diesel formed from plant oils or fats.

What is heat pump technology and how do we use it?

Heat pumps allow us to capture cooler (low grade), waste heat in our factories and use compression to convert it into hotter (high grade) heat that we can then reuse in our manufacturing. For one unit of electricity consumption, we can get three to four units of useful heat.

There are two main types of heat pumps – water source and air source. We use both within our operations. For example, in some of our factories, we’re using water source heat pumps to recycle waste heat produced by our air compressors, chillers, and ammonia systems, saving us money and energy. When a waste heat source is not available nearby, then we deploy air source heat pumps.

What challenges do we face as we work towards 100% renewable thermal energy by 2030?

We’ve looked at almost all the available renewable energy sources and there are challenges with many of them. Green (renewable) hydrogen is expensive and won’t be a viable solution at scale before 2030. Geothermal technology is a very site-specific solution and solar thermal is restricted by the space availability at the site. That’s why heat recovery combined with a heat pump, supported by an electric boiler, is the technology we currently favour. It is a proven and reliable solution which can provide uninterrupted heat.

That said, most of our sites are currently using steam, so switching to use heat recovery and heat pump technology means shifting from steam to hot water, which requires a lot of modification to our existing energy distribution networks. Making all these changes in an existing operating factory is complex and can be expensive.

How can we overcome these challenges?

Working out how our targets can be achieved without incurring extra operational costs, or potentially in a way that even makes savings, is a key part of our plans to adopt renewable thermal energy. It’s worth noting that although investing in a heat pump is more expensive than an electric boiler initially, the operating cost is much lower.

We also need to ensure there are other technologies in place to support the heat pumps, such as electric boilers or solar thermal. At Unilever, we make products in batches, so our demand for heat goes up at certain points in the production cycle, then it stops, meaning heat demand regularly fluctuates. Heat pumps are not like boilers in terms of their ability to respond immediately when demand ramps up. We use heat demand pattern studies to ensure we can cater to peak loads.

How are we working with different Business Groups to switch to renewable thermal energy?

The good thing is most of our processes need heating and cooling subsequently, which helps us in our aim of creating circular energy in our factories, recovering and recycling heat, removing the need for external heat supplies. However, the percentage of captured or recovered heat versus our heat demand varies from 30% to 100% depending on which product category we are talking about. At Personal Care sites, it’s about 30% to 35%; in Ice Cream sites, it can be 95% to 100%.

Our Home Care detergent towers need air that’s heated to around 400°C. Heat pumps are not designed to deliver air that hot, so at present, we have to fall back on options like biogenics to meet that demand. In these cases, we’ve taken steps to ensure that the biofuels we use come from sustainable local sources in line with Unilever’s policy on biofuels (PDF 110.51 KB), and we will also continue to work on longer-term solutions.

What kind of innovative approaches are we taking?

So far, we have developed the know-how for capitalising on almost all types of waste heat from our processes and utilities, through air compressors, cooling towers, and ammonia systems combined with heat pumps. Now, we’re actively working with factories to develop fully integrated energy systems that also include renewable energy solutions, such as solar and geothermal, to achieve 100% thermal energy decarbonisation.

We have trialled integrating heat pump technology with an existing solar thermal system in one of our Personal Care factories in Dubai to provide an energy boost during the night when there is obviously no sun. It resulted in a further 16% reduction in gas consumption, so we’re keen to keep experimenting with the idea of combining heat pumps with other technologies.

We’re also working on recovering heat from wastewater treatment plants with specially designed heat exchangers. We’re exploring ways we could create heat pump solutions to provide 120°C hot water and steam, which will unlock many opportunities without altering existing processes.

We’re using digital tools to improve energy efficiency, such as Internet of Things (IoT) control devices and artificial intelligence (AI) to identify changes in production on the factory floor, acting on sources of waste heat, or shutting down machines when they’re not needed.

Is there anywhere that we’re really leading the field?

One project that is pushing boundaries is our work testing biodiesel in backup diesel generators. Most of our factories have a diesel generator that acts as a backup if there is an interruption in electricity from the grid.

Because we use a specially formulated second-generation (non-food sourced) biodiesel, we’ve been able to gradually increase the percentage we’re using, from 10% up to 20%, and we’ve even run successful trials for using 100% biodiesel. And because we’ve ensured the quality of our biodiesel is so high, we’re now planning to roll it out to all our Indian sites as a next step. As far as we know, nobody else has managed to make a 100% switch yet, so that’s something we’re really pleased to be doing.

One of my key responsibilities is bringing innovative solutions to the business and I’m very proud that we’re deploying the latest technologies wherever possible. We know that in order to reach our climate targets, we need to make big and bold changes. I work for the moments when I help provide solutions that will 100% decarbonise a factory, because we know we need to deliver results fast, and we’re working hard to make that happen.