Sustainable Solutions for Hot Water Production and Water Conservation
As I have previously mentioned, I live in Lake Tahoe, CA. Although it has been abnormally warm this year (60 degree spring-skiing days in January!), the water in our house runs SO cold for SO long! Since we keep the house at a pretty chilly temperature, this icy water makes for a very unpleasant hand washing experience.
Despite doing things like brushing my teeth and letting the water drip for the cat (my crazy Bengal refuses to drink anything but water from my own drinking glass or a running faucet!) BEFORE washing my hands, the water still needs to run for far too long to get warm. Or I have to suffer and have freezing cold hands! I have also heard many people complain about how cold the water is in the public bathrooms at the ski resort.
People in cold ski towns don’t like cold water. So, I decided to learn more about sustainable ways to heat water and reduce the use of un-used, cold water.
A few facts about unused water waste:
-Running the water for a few minutes, even with low-flow fixtures, wastes approximately 3-5 gallons of water. For a family of four, that is about 15,000 gallons of water a year.
-If someone drinks the recommended 8 cups of water a day, that is only 185 gallons of water needed per year. Meaning, just by running water, waiting for hot water, you could be wasting about 20 times the amount of water you drink per year.
-Running hot water is a huge energy drain! Running your faucet with hot water for 5 minutes is equal to the energy usage of a 60-watt light bulb for 14 hours!
The good news is, there are many ways to maximize water and energy efficiency for hot water. These include using low-flow water fixtures, insulating hot water tanks and piping, planning hot-water tank placement to minimize piping, using EnergyStar and WaterSense rated appliances, and being conscious of water usage when taking showers, brushing teeth, washing dishes and laundry, etc.
In addition to all of these improvements, there are a lot of choices to make when deciding what the best type of hot water heater to use (tankless, on-demand, re-circulating systems, solar-hot water… the list goes on). For this blog I am going to focus on residential hot water, highlighting one system for energy efficiency and another system for water efficiency.
One of the most sustainable methods for heating water is solar thermal (heating water using solar radiation). This is discussed in Sustainable Infrastructure: a Guide to Green Engineering by S. Bry Sarté. This heated water can be used for residential hot water, hydronic radiant floor-heating systems, heating swimming pools, and even commercial electricity generation. A typical solar hot water system can provide enough hot water for the average home.
Solar thermal collectors are generally black coils filled with water, which are installed on the roof. The water heats up in the sun and then is stored in a tank until needed. Systems are almost always constructed with an auxiliary water heating system that is activated if the water drops below a set temperature so that hot water is always available. Solar thermal hot water generation is a relatively cheap system, much less expensive then solar photovoltaic panels used for residential electricity generation, so they can be a nice place to start when greening your home.
Solar thermal systems can be passive or active. Passive systems use convection to naturally move the warmer liquid (water or a antifreeze heat transfer fluid) to the storage tank and cold water to the collectors for heating. These systems are simpler and less costly than active systems but can only be used in moderate, sunny climates.
Active systems use pumps to move water from the collectors to storage tanks. This allows the tank to be situated under the collectors, which can increase efficiency since it can be stored indoors in a more insolated space. A controller is also used to ensure that water is only being pumped when the water in the collector is warmer than in the tank. In addition to increased efficiency, active systems have less risk of overheating and freezing because of the tank location and the use of a controller.
Because I am concerned with just how much water I have been wasting while waiting for hot water, the water efficiency technology I was most intrigued by is the hot water demand/cold water return system. This system works by returning cold water to the heat source, instead of letting it drain, becoming waste water. I found that the Chilipepper pump website had some of the best explanations on how the method works, so I encourage you to learn more by checking it out.
Basically, when you go to the sink you turn on a pump that begins drawing hot water from your water heater (these work with any type of heating/storage system). Water going through the pump is returned to the water heater until the pump sensor detects water temperatures above a set temperature. At this point the pump will turn off and allow the hot water to flow to the faucet.
These pumps also draw water faster than most fixtures, especially new low-flow faucets and showerheads. This means that the outlet will receive hot water much more quickly than without the pump. Also, since the water isn’t being wasted while waiting for it to heat up, you don’t need to be concerned about the high flow rates.
There are so many other ways to save water and improve energy efficiency with hot water. This blog would be way too long if I explained them all! I encourage everyone to research the topic more. Point of use water heaters or a tankless heater might be a good way to green your hot water heating system. The EPA also has a great program called WaterSense, and I encourage you to look at their website; it is filled with suggestions on how to reduce water-waste. Limiting hot water use, using sustainable methods to heat water and not wasting unused water all help to make a home environmentally friendly. I hope the methods mentioned above are helpful and jump-start your thinking about hot water usage!
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