If you live in a hot, dry climate like much of Australia or the southwest United States, grey water recovery and reuse makes a lot of sense. Just about anywhere, heat recovery from waste water makes sense, but most systems like the power pipe or the eco-drain only work while you are in the shower, using water at the same time as you are pouring it down the drain.
The Nexus eWater system is a whole different thing. It starts with a grey water collection tank that collects water and cleans it a bit, enough to use in the garden or for flushing toilets. That could be water from the shower, bath or laundry, water that is often quite warm.
This is where it gets cool, or should I say hot. Inside that grey water tank is one end of a heat pump, that actually sucks the heat out of the water in the tank and delivers it to the other end that heats the hot water tank. It pulls so much heat out that it reduces the electrical consumption of the hot water tank by 70%.
Founder and chief technology officer Tom Wood defined the problem in his patent:
With the energy embedded in potable water, through purification and distribution, accounting for a significant proportion of global energy generation—the ‘water-energy nexus’—opportunity exists to target both problems in an integrated way.
He notes that 15% of US carbon emissions come from pumping, purifying, heating and treating water.
More surprisingly, residential water heating accounts for 58% of water-related carbon emissions – 9% of total US carbon emissions.The problem is even worse in water-scarce regions such as California, where 20% of all electricity and gas consumption is linked to a water-related activity.
This joining of a grey water system to a heat pump water heater is really clever for a number of reasons. Even in California or Australia, it is hard to justify the cost of a grey water recovery system on its own. However when you hook it up to a heat pump to make your domestic hot water, it could save you as much as $200 a month in energy and water costs. That pays for itself very quickly- they estimate in under three years without incentives.
But there are good reasons for governments and utilities to give incentives; it reduces sewerage flows by up to 70%, reduces water demand, and reduces peak electricity demand.
According to Bob Hitchner, the chief sales and marketing officer, the system is going through the final stages of UL approval, and is available for order now. These should fly off the shelves. More at Nexus e Water.
See previous best in show selections, most of which are also pretty boring looking but great ideas: