Clothes Dryer Heat Recovery Systems

by Tim Fulton on December 17, 2012

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Lately there has been a lot of discussion on the topic of clothes dryer heat recovery systems. I thought our blog readers might be interested in hearing about some of the ideas that our forum users have come up with.

Many different techniques have been discussed. The first mentioned is simply a finned aluminum tube that would radiate heat into the room. There was discussion of a thermally activated fan to improve heat recovery.

Another design brought to us via a youtube video (shown above). It shows a 55 gallon drum used as a heat exchanger. This is the only prototype that has some decent data that I’m aware of. As you can see, he is recovering a fair amount of heat with this relatively simple system.

heat exchanger
Image from Builditsolar.com

Yet another design GaryGary (a forum user) is considering, is using a DIY version of a HRV type cross flow heat exchanger. GaryGary has already run some interesting tests showing that one load of laundry has roughly 4.5 kWh of heat available for recovery. That is over 15,000 BTUs. He claims this is his largest single electric load in his house.

So, if you have any interest in dryer heat recovery I’d suggest taking gander at the forum and see if anything looks like it might work out for you, or help others work out their system.

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Eco-Modified Refrigerator Saves Energy & Money, Part 2

by Tim Fulton on December 10, 2012

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Last we looked at forum user Ecomodded’s fridge, he had added some additional insulation to it. This resulted in a very impressive 38%. That was only the first step though. He had a few additional modifications planned.

fridge

The next modification was adding a vent to the back of the fridge. The vent’s purpose is pretty simple. Ecomodded’s fridge has a fan that blows air over the heat exchanger coils. This air is drawn in from the bottom of the front of the fridge and exhausted out of the back of the fridge. The vent now directs the warmed air into the closet behind the fridge which keeps that warm air away from the fridge.

fridge

In addition to the vent, Ecomodded also added a flap in the fridge to hold some of the cool air in when the door is opened up. This is made from the same foam that was used on the outside of the fridge. It is flexible enough to still get at the food.

fridge

Last, but not least, he also loaded up the fridge with additional thermal mass in the form of water bottles. This helps displace cool air when opening the door and reduces short cycling.

All of these modifications resulted in an additional 14% reduction beyond the 38% initial reduction. The end result is a pretty nice .7 kWh usage per day. This was measured in the end with a kill a watt.

For more information on Ecomodded’s fridge, see his forum thread.

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Eco-Modified Refrigerator Saves Energy & Money, Part 1

by Tim Fulton on December 3, 2012

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User Ecomodded has been working on doing things to improve his refrigerator’s efficiency for the past month or two. Thankfully he has gone step by step measuring his energy reduction as he goes along.

fridge

The first thing he did was cover the back, sides, top, and area around the compressor with SolidBlack–MD Flooring Underlayment. It is actually a sound deadening floor underlayment. However, it has an R-value rating of R3.3 per inch. He stacked four layers of this material up and adhered them to the fridge with some spray adhesive.

fridge

The last layer was a blue vapor barrier which is a thin foam material.

fridge

With these modifications, Ecomodded noticed his freezer temperature dropped from 0F/-18C to -10F/-26C. To compensate he readjusted the temperature setting from about halfway to about 1/5th to get back to 0F/-18C.

The before and after testing was done without a kill-a-watt, so there are no kWh savings calculated. However, Ecomodded measured the compressor’s time on/off. Before the modifications, the compressor was running for 35 minutes every hour and a half. After the modifications, the compressor was running for 26 minutes every two hours. This is a 38% reduction in on time and translates to just that in energy savings.

Another added benefit of the sound deadening is that the compressor is much harder to hear now.

For more information on Ecomodded’s fridge, see his forum thread.

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Year Round Greenhouse

by Tim Fulton on November 26, 2012

greenhouse

Forum user Acuario has built himself a greenhouse that is usable for the entire year. It is roughly 140 square feet (13 square meter), and is built attached to a shed. In winter, the greenhouse is kept warm via its own solar gain, plus some solar hot water panels that circulate water through pipes buried in the dirt. The whole thing is controlled by a DIY electronic controller.

green house

Construction isn’t incredibly complex. It has a brick base. The greenhouse itself was a kit that Acuario bought. It is mostly aluminum and polycarbonate. As you can see, the hydronic heating coils are just laid below everything.

green house

green house

With the greenhouse built, Acuario went about designing a control system to automate many of the greenhouse tasks. The controller is designed around a PIC16F877A development board. This takes care of nearly all the routine things from the solar heating, to the grow lights, and even watering the plants.

green house

The one thing Acuario is still working on is a cooling setup for those hot summer days. The plan is to use some temperature sensors and fans to also automate the cooling system.

green house

To top it all off, the greenhouse also requires no energy to maintain itself. In addition to the solar hot water heating setup, it also has solar PV (electric) panels to take care of powering the lights, pumps, and controller.

For more info on Acuario’s greenhouse, see his forum thread.

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Air Source Heat Pump Water Heater DIY Install

by Tim Fulton on November 19, 2012

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Xringer has finished up yet another project. This time around he has installed an air source heat pump water heater called an A7 AirTap. Its a retrofit kit that allows you to add a heat pump that is installed on a conventional electric hot water tank (or any water tank really). The AirTap will be used in an effort to reduce/eliminate the use of his oil burning boiler which is quite expensive to run.

So, lets take a closer look at how this water heater operates. It is a heat pump, which means it only moves heat around. It does not create heat like a regulator water heater would do by using an electric heating element or a gas, wood, or oil burning does. This operates exactly how a conventional air conditioner does. It moves the heat from in your house to the outside. In this case the AirTap is moving heat from where it is and putting that heat into the water tank. Xringer has the tank located in his basement. He is hoping that a side effect of using the water heater is some dehumidification of his basement.

water heater 1

So, lets get to the installation. First step was to find a hot water tank. Xringer decided on an inexpensive 40 gallon GE electric water heater from the local big box store. The water heater was put into the desired position with a drain pan under it.

water heater 2

The next step was adding the AirTap mounting brackets and pipe fittings to the top of the tank.

water heater 4

With the water heater ready to recieve the AirTap, it was mounted on the top of the water heater. To get the heat into the water tank, the heat exhanger needed to be inserted. This comes in the form of a copper tube that is pushed in through the an opening in the top of the tank.

water heater 5

Once the tube is fully inserted, the top of the pipe is sealed with a special nut that makes everything water tight.

water heater 6

With the bulk of the install done, all that is left to do is install a drain so that when the AirTap condenses any water, it has a place to go.

water heater 7

And, last but certainly not least, you have to connect the inlet and outlet to the water tank just as you would any ‘ol water heater.

A nice feater Xringer decided to add was a bypass so he can opt not to use the heater if he decides it doesn’t work well in winter time. Pulling heat out of a cold basement may not be the best option. We’ll see how that works out come winter time.

For now, the heat pump water heater has been working amazingly well for Xringer. During the Summer and Fall months so far, the AirTap has been using a little less than 1 kWh per day to provide Xringer and his wife with hot water. This is opposed to using 1/2 a gallon of heating oil. During his two month update, he noted that he has saved roughly $125 in heating oil by switching to the AirTap.

For more detailed info, see Xringer’s thread on the install.

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