Mixergy Water Storage. Smart technology for grid stability. Latest Info In The World

 One of the most common questions I get asked by you good folks out there is "what can I do as an individual to reduce my own carbon footprint?" It's a very good question, and nowhere is it more relevant than in your own home. In the United States, households account for more than 21% of the total energy mix. Here in Europe it's more than 27%, so finding ways to reduce your domestic energy consumption is one of the most impactful actions you can take as part of your contribution towards climate mitigation. Things like solar PV, ground or air source heat pumps, and even the possibility of hydrogen as a fuel source. All those options look set to become more commonplace as we move towards 2030, and hopefully the more enlightened governments around the world will put in place very healthy incentives and subsidies to help and encourage us all to make the change. 

A great deal of development work is also being carried out to produce smarter, more efficient household products and systems that can help us all achieve our carbon footprint reduction goals, and one of the most impressive designs I've come across in recent months is an intelligent hot water storage system from a UK company called Mixergy. I caught up with the folks at Mixergy recently to find out how their technology can not only cut down your energy consumption and save you money, but also contribute towards electricity grid stability as we move towards greater reliance on renewable but intermittent forms of energy like wind and solar. Hello and welcome to just have a think.

 If you've got a water storage tank in your house you may well have experienced the frustration of coming home after being away and having to wait ages before you get any hot water through the taps, or perhaps the other delight of stepping into the shower only to find that someone else in the house has used up all the hot water having a nice luxurious bath. One of the main advantages of the Mixergy system is that it only heats up what you need. That means it produces usable hot water about five times faster than a standard tank. Inside the mixer cylinder there's a fairly standard heating coil transferring heat, in most cases, from a gas boiler. The difference here is that the coil is at the top instead of the bottom. This means that initially only the top slug of water gets heated up. 

 There's also an electric immersion heater up there which we'll come back to in a moment. One of the thermal properties of water is that while it's very good at moving heat from a surface via convection, it doesn't like transferring heat downwards into a colder section of water via conduction. So, unless there's some physical mixing or stirring of the hot and cold water in the tank, then the warmer water tends to stay warm and the colder water stays cold. And for the technically mining among you that junction between hot and cold is called the thermocline. So the coil heats the top section of water to the desired temperature of say 50 degrees Celsius then a pump starts moving cold water from the bottom of the tank up to the top at a precisely controlled flow rate so that the   energy balance of cold water going into the hot section matches the heat input, which then stops   the temperature going up any further.

 If that cold water was pumped straight out of a pipe then the system wouldn't work because the water would just sink straight back down to the bottom, taking some of the hot with it through physical churn, so the cold is transferred into the hot via a diffuser that spreads the water out like a mist allowing it to very rapidly achieve the   same temperature as the hot water. Effectively the tank is heating from the top down instead of the   bottom up. And that clever arrangement results in reduced heat losses. Overall the Mixergy tank can save up to 20% on energy consumption through a combination of those reduced losses and better   control of the energy source heating the tank. And as you'd probably expect there's a smart app that   allows the householder to see exactly how much hot water is available at any given time and operate   the heating controls remotely. It even works with voice control via Alexa or Google assist. 

But the Mixergy software is also smart enough to learn the patterns of behavior of the   householders, and it uses that information to work out the optimal times to pre-heat the tank,   which in most cases is best done at night time using low or even negative tariff electricity rather than gas. Which brings us to that electric immersion heater element I mentioned earlier. This chart shows a typical night-time heating cycle for a Mixergy tank on a   flexible energy tariff. Mixergy's cloud software is constantly talking to the energy supplier   and it can see when the electricity supply price goes negative. Normally this tank would   be receiving heat from the system gas boiler, but in this case between 2am and 2.30am the consumer is actually being paid a small amount for every unit of electricity they consume.

 So instead of   using gas, the Mixergy system takes advantage of this situation and starts using that electricity   to heat the tank via the immersion heater. Same thing between 2.30am and 3am, then the electricity   price goes back into positive territory so the tank stops consuming for half an hour,   coming back on again at 3.30am when the consumer gets paid 1.34 pence for every unit consumed.   Another pause at 4am, and then a final spurt between 4.30am and 5am, by which time the water   at the top of the tank is well over 60 degrees Celsius. And because of the astonishing level   of insulation that modern materials provide, the tank stays very close to that temperature   for the rest of the day. That opportunistic use of electricity means the tank is sometimes being   paid to heat. 

Plus you get the benefit of switching between gas and electricity   which is something that will most likely become more and more desirable as the grid decarbonizes. But the smart features don't stop there. Because the Mixergy software is capable of monitoring   the frequency and voltage of the electricity supply, it can make the water tank function a bit like a battery to help stabilize the grid through a mechanism called frequency response. We looked at that in detail in a previous video, and you can click up there somewhere   to jump back to that one. In basic terms though, the transmission system operator, which in the UK   is the National Grid, predicts national energy consumption on a half-hourly basis throughout the day and night and prices are set accordingly to incentivize generators to either turn up or turn down their production during each half-hour segment.

 Once that's set, it's pretty much fixed, so if something unexpected happens during a half hour slot that increases or decreases demand you need to either find extra power or dump unwanted power. Not enough power could lead to blackouts   and too much power could lead to, you know, blowing up your substation - which you don't want! That mechanism corrects any imbalances between supply and demand on a half hourly basis, but   other totally unpredictable events can also happen from one minute to the next. Things like a power   station breaking down or a large surge in wind power that wasn't forecasted. During those brief   events the grid frequency rises or falls depending on whether there's a surplus or deficit of power. Because Mixergy tanks can measure that frequency they can respond to those momentary fluctuations,   and one of the great benefits of that is that they can help the grid accommodate more renewables on the system. Mixergy's early field trials demonstrated that the vast majority of consumers   rarely use more than fifty percent of their water tank's capacity when measured. 

That means there's an opportunity for the grid operators to dump excess energy into Mixergy's   water tanks, very similar to the way that utility scale battery systems are now being used. Mixergy now have just over a thousand of their tanks installed across the UK providing about   one megawatt of frequency response capability. If all the existing water tanks in the UK were converted to this smart technology then they could provide about a hundred gigawatt hours of storage   capacity. That's more than 10 times as much as the UK's largest pumped hydro facility at Dinorwig in North Wales. And, unlike batteries, these tanks don't care about the number of cycles they're   put through either.

                      

 There's no degradation in the heating system capacity over time,   and in the unlikely event that an element fails then it can simply be swapped out without having   to replace the tank or any of the other hardware. Mixergy provide a 25-year warranty on their tanks   but they expect them to last way longer than that. The tanks can fully heat and discharge   up to three times a day, so over a 25 year period that's potentially tens of thousands of cycles. To future proof the technology as we move towards a net zero carbon world in 2050 the tanks have been made compatible with any kind of power source including rooftop solar PV systems, which can divert excess solar power into the tank instead of exporting it back into the grid,   and of course the heat pumps that the UK government are extremely keen for households  to adopt over the coming years. The target is for 600,000 heat pumps to be installed in UK  homes by 2028.

 Quite how the government intends to subsidise this mass transition away from gas is probably the subject for a future video, but if they succeed, and hopefully they will, then   the Mixergy tank is ready. It's got a pre-fitted port that can accept a little plate heat exchanger to allow the system to work seamlessly with this new technology even if they've   initially been installed with a gas boiler or electric immersion as their main heat source. Now a question that you might reasonably ask is how these tanks compare to combi boilers in terms   of efficiency for hot water supply, especially as the world moves to greater urbanization and people   transition to smaller living spaces in apartment blocks. Combi boilers don't use storage tanks,   they take water from the mains and pass it across a heating element, in theory to provide instant   hot water whenever it's required. And it works perfectly well, especially for smaller dwellings.

But in 2019, Mixergy worked with a research team at Oxford university to conduct a study comparing   the working efficiency of a market-leading combi boiler and a market-leading storage tank from   one of their competitors. That study found that the combi boiler was only 73 percent efficient   compared to just over 84% for the storage tank. And in fact the smarter system in the Mixergy   tank actually achieves an efficiency of just over 95%. The reason for that discrepancy between tanks and combis is the fact that a lot of the time we consumers turn on the hot tap very briefly just to wash our hands or rinse a plate or something. When we do that the combi boiler clicks on and takes a bit of time to get the water flow up to temperature.

 In fact sometimes the tap is on so briefly that the boiler doesn't have enough time to get the water up to full heat, so a lot of energy has been invested just getting the heat exchanger up to temperature, and once   the tap is switched off again all that energy just goes up the boiler's flue and out to fresh air. Other smart technologies are now coming to market too, like heat recovery systems that divert hot shower drainage water back into the heat exchange pipes to pre-warm the cold water supply going into the mixer tap. That means much less hot water is needed from the tank in the first place, which of course means the tanks can be made more compact to fit into smaller spaces in those urban apartments. Mixergy have also experimented with the other option for providing hot water for apartment blocks which is to have large communal water tanks for the entire building.

   They recently supplied two10,000 litre tanks to London's Southbank University as part of a project   exploring the potential of harvesting geothermal energy from an existing aquifer in Central London. And the performance results of that project will be analyzed very thoroughly to help inform any   future development work. Mixergy aren't confining themselves to the UK either. They're working with   a very large manufacturer in France to provide systems for the French market, and in July 2021   they'll be shipping a hundred of their tanks to a holiday resort in Sochi in Russia.   Theoretically there's no reason why this technology couldn't be employed anywhere in   the world, providing household consumers with the benefits of greater efficiency   and control over their hot water supply. And that all-important frequency response facility   has the potential to play a vital role in helping to accelerate the integration of renewable energy   sources into the distributed smart grids of the future.