World News | Storing renewable energy with electric water heaters could do the work of 2 million home batteries — and save us billions

Sydney, June 5 (Dialogue) Australia’s energy transition is well underway. Roughly 3 million homes have rooftop solar and sales of midsize electric vehicles have surged.

But as we work towards an all-electric home powered by renewable energy, are we overlooking a key enabling technology, the humble electric water heater?

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About half of Australian households use electric water heaters, while the rest use gas. So what’s so great about electric water heaters?

Electric water heaters provide an inexpensive way to store large amounts of energy in the form of hot water. A heater with a 300-liter tank can store as much energy as a second-generation Tesla Powerwall at a fraction of the cost.

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Our research at the UTS Institute for Sustainable Futures found that Australians use domestic electric water heaters to store as much energy as more than two million such batteries in households.

This could ultimately save us more than A$6 billion a year in energy bills while moving us closer to net zero carbon emissions.

Our report, released today and funded by the Australian Renewable Energy Agency (ARENA), recommends that policies are urgently needed to rapidly replace gas with ‘smart’ electric water heaters in order to halve emissions by 2030 and reach net zero by 2050 water heater. Smart heaters can be turned on and off based on changes in electricity supply and demand across the grid.

This means that these heaters can absorb excess “off-peak” renewable energy, especially solar energy, helping us solve two critical problems at the same time. They can help reduce and eventually eliminate greenhouse gas emissions. They can help balance fluctuations in renewable energy supply by providing flexible demand, making our grid more stable.

emission reduction

There are three main types of electric water heaters. Traditional “resistance” heaters use electricity to heat water directly. Solar water heaters use sunlight and electricity, but have become less popular with the advent of newer “heat pump” devices.

They collect heat from the air and “pump” it into the water. Heat pumps use three to four times less electricity than resistance heaters.

Back in 2010, electric resistance electric water heaters typically produced about four times the emissions of equivalent gas-fired water heaters. Heat pump emissions are about the same as gas emissions. That’s because electric water heaters consume a lot of electricity, and most of them are produced by burning coal.

This is changing dramatically as we generate more electricity from renewable sources.

The Australian Energy Market Operator, AEMO, regularly publishes updated pathways to a clean energy future. In the most likely outcome, the “step-change scenario”, natural gas becomes the most greenhouse-intensive hot water option by 2030.

By 2040, once the transition to renewable electricity systems is largely complete, emissions from resistive and heat pump water heaters will be significantly lower than their gas-fired counterparts.

Water heaters can last 15 years or more. So the stock of heaters in our homes for the next twenty years depends on what we have installed today. Therefore, replacing gas heaters with electric heaters should be a top priority of our energy transition.

Our work explores a range of scenarios, each with a different combination of water heating technologies. One is a business-as-usual baseline where gas water heaters are still prevalent. In the alternative scenario, natural gas is phased out over the next 10-20 years.

We’ve found that replacing gas with electric water heaters not only helps us get to net zero faster, but also saves us money.

Natural gas is expensive, and it’s unlikely to get any cheaper. Abundant renewable energy sources provide excess cheap electricity that water heaters can help absorb. Seizing this opportunity could save us more than $6 billion a year in energy bills by 2040.

Improve grid stability

Solar and wind are now the cheapest generation technologies we’ve ever had. But to maintain a stable electricity system, we need to match demand with fluctuating supply from renewables. Batteries provide part of the solution, but are still relatively expensive.

Electric water heaters offer a cheaper way to store large amounts of energy and provide the demand flexibility that the grid requires.

Our study found that a scenario emphasizing demand flexibility using smart electric water heaters could provide an additional 30GWh of daily flexible demand capacity compared to a conventional baseline.

This equates to more than 2 million household batteries on the National Electricity Market, which supplies electricity to eastern and southern Australia.

Back to the future of water heating

Since the 1950s, “off-peak hot water” has seen Australian electricity suppliers turn off domestic water heaters during the day and turn them on at night to better match supply and demand. In return, customers receive heavily discounted prices.

We’ve moved away from using off-peak electric hot water in recent decades as incentives have diminished and more homes are using natural gas.

When we power hot water, which technology should we use: resistance or heat pump? The answer is a little bit of both.

Our study explores the trade-offs between highly flexible electric resistance water heaters and highly efficient but less flexible heat pumps.

Heat pumps use less electricity and are cheaper to run. Where electricity prices are high or where electricity flow is limited, it makes sense to use a heat pump. However, they come with a higher upfront cost and are not suitable for every home. For example, many apartments do not have access to suitable outdoor space.

And because they use less electricity, heat pumps offer less flexibility to demand. As renewable energy, especially solar energy, increasingly feeds our grid, the ability of resistive electric heaters to absorb excess “off-peak” renewable energy is a great advantage.

With the right policy and market reforms, we will all benefit from a system that again rewards customers with cheap off-peak electricity in exchange for network operators being able to turn our water heaters off and on as needed. (dialogue)

(This is an unedited and auto-generated story from a Syndicated News feed, the content body may not have been modified or edited by LatestLY staff)