Forum user solarhotairpanels put together a very nice DIY solar hot air panel construction guide. He goes over his first design, and how he went about improving it for his next few panels. He lays out all the steps so you can follow along and make your own solar hot air panels yourself. He even goes over wiring up the fans. Its a very nice write up, check it out!

Here are a few images from his guide:

Do you have some windows that you just use for light, but never really look out of? These are a perfect fit for adding some additional insulation to. One such inexpensive method is using bubble wrap. It still lets light through and is cheap and easy to install.

But, is it worth it? How well does it work? A couple of our forum members have taken it upon themselves to do some testing and share it with us.

AC_Hacker did a quick test setup with an IR thermometer. His images are shown in this post.

He bought a 24 inch wide roll of bubble wrap for $15. This is enough to cover three or four windows. When tested on a single pane window with no storm window, he said there was a pretty sizable improvement. The single pane of glass measured 47F / 8.3C without bubble wrap, and with two layers, the inside surface measured almost 56F / 13.3C.

AC_Hacker also tested the bubble wrap on a single pane window and a double pane window filled with argon gas. He said they each showed a lessening impact having the bubble wrap on them.

These were his conclusions:

• If you have single-glass windows, bubble-wrap can certainly help. At $15 for several windows, it is tremendous bang for the buck.
• If you have single-glass with storms it will help a little.
• If you spent $300 on Argon filled double low-E, don’t bother to invest $15 to cover your Argon-filled windows with bubble wrap.

However, I’m sure I’m not the only one with a box laying around somewhere with some bubble wrap in it. Finding some for free shouldn’t be a big issue. So, you should be able to do this for free.

Gary Reysa also did some testing with bubble wrap quite a few years ago and shared his results with us. His tests were done on double pane windows with a low-e coating on them. He also used an IR thermometer to take his temperature readings. His results showed a 45% reduction in heat loss. Very respectable. It looks like he used bubble wrap with the larger bubbles on it compared to AC_Hacker’s bubble wrap with little bubbles.

So, if you have windows you just use for light, consider putting some bubble wrap over them. Its extremely easy to do and Gary even has an installation guide on how to do it on his site.

Niagara Conservation is exactly what it sounds like, a company that puts out products for conserving. Conserving what? Well, Niagara has a real nice selection of things. They have water conservation products like ultra high efficiency toilets, low flow showerheads and faucet aerators. They also have electricity conserving products like smart power strips, CFL lightbulbs, LED nightlights, water heater insulation blankets, and tools like a refrigerator/freezer thermometer to see if your fridge is too warm or too cold. In addition they have weatherization products that help reduce your heating/cooling bill like weather stripping, programmable thermostats, window film kits, and more. Seriously, check out their site for the full gambit.

For the giveaway, Niagara has donated their Earth low flow showerhead. It is rated at 1.25 gpm which may not seem like much, but you likely won’t be able to tell. The showerhead has three spray settings: needle, massage, and a combination of the two. The reviews I’ve seen for this showerhead are quite good. Thank you Niagara Conservation!

Waterpik is a company that sells a small assortment of products including showerheads, water flossers, sonic toothbrushes and neti pots. From an energy reduction standpoint we’re going to focus on their showerheads. Waterpik has a line of EcoFlow showerheads that can save you some water, and with showers that is hot water that you’ve spent lot of energy heating up. They offer most of the showerheads with a fix head or in a hand held version. All of the heads they offer have multiple spray settings, and some have as many as seven settings.

For the giveaway, we have Waterpik’s ECO-533 showerhead to offer. It is a 1.5 GPM showerhead and it offers 5 different spray settings. Thanks Waterpik!

Homepower is a magazine that basically covers everything we’re about here at EcoRenovator. They cover the gambit of energy efficiency including topics like solar, wind and hydro electricity generation, solar heating, general energy efficiency, building & design, DIY projects, and even some alternative transportation topics. They even offer some of their articles online for free. Of course the good ones are reserved for subscribers. That is where our giveaway comes in. If the winner so chooses, s/he can get a one year digital subscription to Homepower. This not only gives them one years worth of Homepower article, but also a pretty large history of articles over the past few years. Its quite a large and useful vault of knowledge. I can speak from experience as a subscriber for a few years now.

Homepower has donated a 1 year online subscription for the EcoRenovator giveaway this year. Thank you Homepower!

Hey, it’s fall again! That means it’s time for EcoRenovator’s giveaway for its readers and forum users. You guys provide us with cool things to post on the blog, find and share tons of information on the forum, and really make this site what it is. This is our chance to give something back, and help you guys achieve your goals.

So, how do you win? It’s pretty simple. For veteran forum users, the giveaway will work the same way it has in previous years. If you aren’t yet, you must register on the forum and make a post to enter. Each post you make from November 6th through the end of the month will be an entry into the giveaway. On December 2nd, five winners will be randomly selected from the posts made between now and then. Those five winners will be able to select a prize from the list below. Once the first winner decides what s/he wants, the second winner will be notified and will be able to make their choice, and so on with the rest of the winners.

Giveaway Prizes:

• Black and Decker Thermal Leak Detector *
• HomePower 1 year digital subscription
• Modern Hydronic Heating by John Siegenthaler (1st edition, used) *
• Niagara Conservation Earth® Showerhead – 1.25 GPM MODEL #N2912
• P3 International Kill a Watt *
• P3 International Save a Watt – TV Standby Killer *
• The Energy Detective TED 5000-G whole house electricity meter *
• Waterpik ECO-533 1.5 GPM showerhead

I would like to thank the companies listed above. They have agreed to donate the above items for our giveaway winners!

Good luck to all the entrants!

* Donated by EcoRenovator

First, we found a clock that we wanted to use, then we selected the solar components, and then we tested the clocks power consumption. Next, we are going to start modifying the clock to make it solar powered.

Thankfully, this is really quite simple. We have no charge controller since we aren’t going to charge the batteries very quickly at all. So, we really just need to figure out a way to wire the solar panel to the alarm clock batteries so that when the sun is shining it will charge them.

To do this, we need to pop open the clock and took a look around. We need to find the positive and negative end of the battery pack. Once we find the positive and negative terminals, a wire needs to be soldered to each end. These wires are what our solar panel will connect to.

The wires need to get outside of the case to connect to the solar panel. So in my case, I drilled a hole in the back side of the clock housing. There was conveniently already a nice little boss in the plastic, so I used that.

Lastly, I recommend tying a knot in the wires on the inside of the housing. This prevents them from being pulled and the soldered joints breaking from too much flexing.

On the end of the wires is a standard 3 pin plug like you would find on a computer fan. This will allow me to plug and unplug the solar panel and do some testing easier for our next article on the alarm clock.

For more informaiton, see the forum thread.

At the end of the last article, we had chosen an Elgin 3350E alarm clock, picked out some rechargeable nimh batteries, and selected a solar panel and diode. Now, we dive into some testing that really isn’t totally necessary, but it is fun for us electronic geeks out there, and it will give us an idea of how often the clock will need to bet set in the sun to recharge.

With the alarm clock out of its packaging, it was time to try it out a bit. So, I grabbed some batteries and threw them into the clock. It is a very basic clock. For features, it has one alarm, the date, the clock, and an automatic backlight that only turns on in the dark. Everything works as expected, there is a little photoresistor on the back side that senses when the backlight needs to be turned on. Interesting enough, it doesn’t just turn the backlight on/off. It actually does dim up and down as it gets brighter/darker in the room which is pretty cool and an additional power saving feature for the power saving feature.

Alright, onto the geeky stuff. The main reason for tinkering about here was to find out how much power the clock consumes. So, I hooked up two multimeters to the clock. One measured voltage and the other was set to measure current. With the clock just running in normal daylight (no backlighting), it uses a pretty low 20uA (microamps) at 4.55V.

Next up was testing with the backlight on. Not too surprisingly, the backlight adds a lot to the power consumption. With the backlight on, we get a power draw of 234 uA, an 11X increase! Now it makes sense why those solar alarm clocks don’t have backlighting like this one does.

Still, those are pretty low power draw numbers. The nimh cells that I will be using in the clock are rated at 2,200 mAh, or 2,200,000 uAh. Even with the backlight lit 24/7 it should theoretically power the clock for over a year. For us, this just means that the solar panel doesn’t have to do much to keep up which is a good thing. A few hours of sun a month should be enough to keep this thing running and happy.

In our last article, Hv23t took a scrap electric water heater and dehumidifier and put together a DIY heat pump water heater. However, there are some issues to work out. Mainly, the cold side heat exchangers were freezing up like bricks of ice which decreases efficiency quite a bit. There were also some other features to add to it.

However, even with the setup as is, when Hv23t tested things, he was seeing a COP of 3.1-2.1 depending on the water temperature. The higher the water temperature, the lower the COP as is the nature of heat pumps.

The first enhancement was to insulate the refrigerant lines going to the tank separately. Hv23t measured their temperatures and one was always 30-40F warmer than the other.

The second enhancement was to use a recycle timer to stop the compressor during the defrost cycle. This will stop the ice from forming on the cold side heat exchangers. What this basically does, is stop the compressor from running when ice forms on the heat exchanger. The natural heat in the system and around it melts the ice, and then the system can start running again. Previously, the system kept running until the block of ice had formed, by this time the efficiency is already being hurt. With the recycle timer, the unit will run for 45 minutes, and then turn off for 5 minutes. Previously it ran for 1 hour and 40 minutes before turning off to defrost.

The next thing Hv23t did was install a time delay circuit for the resistance heating element in the heater. Once the heater calls for heat, this timer is engaged and if the heater is still calling for heat in 2 hours, the electric resistance heater kicks in to help warm the water.

The last electrical feature Hv23t added was a temperature controller. This little unit stops the heat pump from running if the ambient temperature is too low. Once the air temperature gets too low, its more efficient to just run the resistance heating element.

Last, but certainly not least, Hv23t installed the heater in his parents house. They previously had a propane hot water heater that was costing them approximately $775 per year to run. With a few measurements with a kill a watt, Hv23t estimates the new heat pump water heater will use around $175 worth of electricity to supply their hot water. A $600 per year savings isn’t too bad for using a bunch of scrap parts!

For more information, see Hv23t’s forum thread.

Forum user BenNelson is up to another project. This time he is doing the two birds, one stone deal. He got his daughter a swing set, but also slapped 400W solar panel on the roof of it! Nice idea Ben.

Ben also runs a site called EcoProjecteer, so I’m just going to point you to his work there. In typical Ben fashion, he has a few videos in additional to some entertainingly written articles to keep things interesting.

Here are the links to the different parts of his install:

• Introduction & getting the swing set
• Solar panel installed
• Reinforcement added to the swing set
• Wiring run

He also started a thread on our forum. If you have any questions or comments I’m sure Ben would appreciate any feedback.

Is your fridge an energy hog? Do you even know how much power your fridge uses? Well, it can be quite a bit. Even the energy star fridges of today can easily use 1kWh per day. Older refrigerators can eat up 4kWh or more. So, how would a fridge that uses .4 kWh and is really cheap sound? Well, that is exactly what AC Hacker has made.

His “freezerator” originally started out as a upright freezer from craigslist for $125. He didn’t want to go the vertical freezer route for convenience sake. The freezer he got was nothing special. It is not even a real efficient model, its not an energy star model. But, freezers in general have a couple things going for them. They normally have more insulation than fridges. They are also built to keep themselves at a lower temperature, so your refrigeration system is probably built to be a little more efficient. These add up to lower power consumption, especially when you use it as a fridge instead of a freezer.

So, how do you convert a freezer into a freezerator? Well, its actually pretty simple to do, and cheap too. All you really need is one of these temperature controllers you see above, and some wire to hook things up. The controller for AC Hackers project was sourced off of ebay for $16. It even has a built in relay that can handle the freezerators power draw.

The new temperature controller simply controls power to the freezerator via a temperature probe that is currently just shoved in through the door opening. Since the freezerator’s original temperature control is set to a much lower temperature, it kicks on as soon as the new controller powers the freezerator up. When the temperature hits the new controllers cutoff point, power to the freezerator is shut off.

The freezerator has been in use for several months now and AC Hacker has been logging the energy use since day one. The average power usage is .395 kWh per day. He estimates that if he had started out with a nicer energy star rated freezer, his power usage would be closer to .275 kWh per day.

For more information, see AC Hacker’s forum thread.

Do you have an old lamp laying around that you like, but can’t find a new efficient CFL or LED bulb to fit? Well, then this article is for you my friend! Forum user Where2 had this same scenario and decided to modify his existing halogen lamp into an LED lamp.

The lamp was one of those halogen floor lamps that were very popular in the 90s. 300W of halogen spewing light (and heat) with a nice little dimmer knob on it. Where2 looked into new floor lamps, but didn’t feel like spending the $40+ on a new lamp when he had something very close to what he wanted already at home.

Instead, he decided to modify the lamp so that it would take a standard LED bulb with a screw base. To do this, he purchased two screw bases at his local home improvement store along with two dimmable 9W LED bulbs (800 lumens each). He removed the old halogen bulb mount, and replaced it with the two screw bases using the same holes that held in the halogen mount. Then, he wired the new bases into the existing lamp wiring. And, then he installed the new LED bulbs in the new bases.

The conversion cost very little. Each screw base cost $3. The rest of the stuff Where2 had on hand (wire, wire nuts, and blade connectors). So, a grand total of $6 was spent on this LED light conversion. The LED bulbs, which would have been needed anyways with a new lamp, cost him $13 each.

Where2 says the dimmable bulbs work good with the dimmer switch on the lamp, and that it provides plenty of light despite the 94% reduction in electricity use! Now, instead of 0-300W of power use its 0-19W. Quite the reduction. And for anyone saying that the new bulbs might not put out enough light, Where2 says that isn’t a problem. His wife uses it as a reading lamp every night and has no complaints.

For more information, you can see Where2’s forum thread.

While I am remodeling my office, I decided to take the opportunity to access some plumbing in the wall and ceiling. I have a bathroom on my second floor, and it takes a long time to get hot water up there since the hot water heater is in the basement.

The old setup was run with 3/4″ copper pipe. This worked well and provided a minimal pressure drop. But, it took almost a minute to get hot water up to the bathroom upstairs. Oh, and it was uninsulated most of the way too.

The choice to replace it with 1/2″ PEX tubing was almost a no brainer once I ran some quick calculations. 1/2″ PEX would only create an additional 2 psi drop versus the 3/4″ copper. After having used it a while now, this isn’t even noticeable. Also, 1/2″ PEX holds less than half the volume of water compared to 3/4″ copper, so the time to get hot water up to the bathroom would be reduced by more than half.

So, it was just a matter of picking up the necessary parts and going to work. The parts were pretty simple. Just a couple copper to PEX fittings, the tubing itself, and some pipe insulation. All in all, it was less than $25 in parts.

After everything was replaced with the PEX the effects were pretty drastic. It used to take 50-55 seconds to get hot water upstairs. Now it takes 20-25s.

Another side benefit is that I can now set my water heater to a lower temperature because the PEX is loosing less heat than the copper did. It used to be set to 140F, and now it is set at 130F.

Overall I’m very happy with the change. So, watch your plumbing sizes when you’re doing plumbing work, especially on the longer plumbing runs.

For more info, see the forum thread.

A little while back I was using my Great Stuff Pro14 foam dispensing gun to do a bit of exterior sealing on the house. While using it I noticed that it slowly started to clog up to the point where the foam was barely coming out of the gun. I didn’t think too much of it since I was getting close to an empty can. However, it just wouldn’t quite stop coming out while the trigger was pulled. This led me to think that the gun was getting clogged internally. I quickly decided to tear the gun apart to see if I could get it cleaned out before it was completely clogged up.

Before we get started, I’ll mention I took all these pictures upon reassembly of the foam gun. I’ll be covering both disassembly and reassembly in the same pictures since there are a lot of pictures. Also, it helps to have a tub of acetone to put parts into during disassembly to stop any uncured foam from curing inside the gun. So, lets get started.

First, remove the foam can from the gun if necessary. Next, remove the screw from the adjustment knob on the back of the gun.

Under the adjustment knob is a plate that is held in with two screws. Remove the screws and the plate.

Unscrew the brass adjustment screw. There will be a steel ball and spring (which is under pressure) behind it.

Behind the spring is another brass part. Notice that it fits into a slot on the trigger for reassembly.

Remove the brass part and the rod. The rod may be stuck in there pretty good. A pliers on the shaft may help to free it, but be careful not to mar the surface of the rod. It must seal against o-rings in front of the trigger when you reassemble things.

With the rod removed, clean it up as well as you can. Make sure not to mar it up and pay special attention to the tip that seals the gun.

Next, remove the foam can mounting piece. It has a hex base so you can use a wrench to remove it.

On the bottom of the mounting piece, there is a brass piece with a slot in it. Use a flat bladed screw driver to remove this piece. Behind it is a spring and a white plastic ball. You might need to remove foam to get to it. I just used a small flat bladed screw driver to scrape it out. Some acetone may help too. Try not to poke too far into the gun. The white piece is a plastic ball that seals things. If it gets scratched up it may not seal.

After things are disassembled, clean the foam off of everything you can. Just be careful not to mar up the sealing surfaces where the plastic ball seats.

Next, remove the tip from the gun. It has a hex section to get a wrench on it to unscrew it. Once it is removed, scrape the foam out of the inside of it. The rod’s tip seals around the hole in the end, so try not to mar that surface.

When you go to reassemble things, I used some teflon tape to help seal things up. I used three wraps and I think a few more would have been a bit better, but mine did not leak.

The tube is the next piece to remove. Again it has a hex section for a wrench. However, I couldn’t remove it with just that. I had to use a channel locks or vise grip type tool to get a good grip on it.

Once it is removed, scrape the foam out of the inside of the tube. You probably aren’t going to be able to clean it perfectly. This is what mine looked like when I reassembled it.

Now, remove the trigger. It has an e-clip on one side. Remove that and the pin slides right out and the trigger can be removed.

Remove the brass piece in front of the trigger. It has two o-rings in front of it, so make sure to remove those as well. If they are damaged at all be sure to replace them.

When reassembling this piece, first just screw it in a little bit. Once the rod is reinstalled, you can tighten it down so it seals properly.

Next up is to clean the handle section of the gun. Its a bit more tricky, but you can work at it from both ends. Clean it out as best you can.

Once everything is cleaned up to your satisfaction, you can reassemble the gun in the reverse sequence.

After this fix, my gun has been working very well ever since. Good luck with your own.

What would you do if you had a bunch of old pallets laying around? The answers would differ from person to person. Some might make neat bookshelves out of them while others might burn them to keep warm, still others might use them to make a composting area. However, forum user Acuario decided he was going to build a chicken coop.

There are no plans available for the coop. Acuario just took a bit of time to think it out ahead of time and went to work. He even claims to be pretty bad with woodworking.

The tools he used to build the chicken coop are:

• jigsaw
• tape measure
• hammer
• electric screwdriver (drill with a bit)
• set square
• staple gun

This article isn’t really intended as a DIY article exactly. But, the design is relatively simple and should be able to be followed from the many pictures below.

Starting with a pile of pallets.

Build the sides up with posts at each corner to nail to.

Don’t forget to add an opening for the chickens!

A sheet of plastic was used to help keep rain out of the coop.

Easy access to the coop.

The chickens seem to like it. It is certainly better than what they can build on their own.

To see more details of the build you can check out Actuario’s forum thread on the chicken coop.

For some time now, the members of the forum have been testing and reporting back on LED lights they’ve bought and tried out. These are almost always some form of retrofit bulb with a standard E26 or similar screw base. However, Opiesche, a forum user, decided to take a different route. He went ahead and make his own fixture for a string type LED light modules.

Opiesche claims these fixtures cost around $20 each to make from the following materials:

• 1/4″ plywood
• A strip of acrylic
• 1/2″ – 3/4″ binding posts and matching bolts
• Adhesive
• Aluminum L-profile
• LED modules
• LED power supply

The first thing that must be done is calculate how much light you want the LED fixture to put out. With the chart above, you can see a standard incandescent 60W light bulb puts out about 800 lumens. Each of the LED modules in the string puts out 70 lumens. So, you need roughly 11 of these LED modules to put out the same amount of light as a 60W fixture. If you want more light you need more modules in the string.

Now that we know how many modules we want, its time to size a power supply. These LED lights run off of 12V DC power, not 110V AC household power, so we need a 12V power supply. According to the specifications of these LED modules, each module consumes .7W (the reseller’s site is wrong). So, if we have 11 modules, we need at least a 7.7W power supply. For safety sake its definitely recommended to round upwards around 10%, so a 9W supply should be the minimum. If you have 3 or 4 of these fixtures running off the same power supply increase the power supply’s output accordingly.

Now, on to building the fixtures. Opiesche started with a 1/4″ thick plywood strip of wood as the backing plate. The shape of the plywood depends on the shape of the fixture you want. You’ll also want to figure out where the mounting holes and mounting points for the acrylic glazing will go, and drill holes for them at this time. Painting the plywood is optional depending on what you want the fixture to look like.

Next, a piece of acrylic is cut roughly 1″ (25cm) larger in each dimension than the plywood piece. Opiesche used a jigsaw with a fine blade to cut it. It is then cleaned and sprayed with a frosted glass spray on each side. Two coats are recommended for a nice frosted look.

Now, you need to figure out how you want the lights arranged. Keep in mind they are all attached, and you also need points to mount the light to the wall with a screw or something, and you also need mounting points for the acrylic glazing. Once you have figured it out, use your adhesive to glue the modules to the plywood. Be careful not to tug on the next module before the first is secure. Opiesche used locktite power grab, and said it worked pretty good.

Install the glazing mounting points. Once they are installed you can set the acrylic glazing on the mounting points and mark out where the holes need to be drilled. When drilling, start with a smaller drill bit than needed and use very little pressure to avoid cracking the acrylic. Once the smaller hole is drilled, move on to the necessary drill bit size and again use very little pressure to avoid cracking.

After the holes are drilled, you may mount the backing plate with LEDs on it to the wall or ceiling.

Finally, cut two pieces of aluminum L-profile to the length of the acrylic or slightly longer. Use your adhesive to glue it to the sides of the acrylic.

Once it is cured you are ready to bolt the acrylic glazing up to the LED fixture and you’re done!

The last step is purely cosmetic, and leaves plenty of room to make the fixture your own design. The trim could be replaced with a wood you like that is painted or stained, or any other material you like. Opiesche even made one without a trim piece around the sides if you’re just looking for a simpler look.

For more info on the LED fixture build, see Opiesche’s forum thread.

Over the last two months or so, forum user Hv23t has been working on a DIY heat pump water heater. It actually started with a scrap run. His neighbors saw what he was doing and asked if he could haul off a few things for them. In the end he was left with a couple dehumidifiers that didn’t work and a few hot water heaters that didn’t have any problems. Instead of scrapping these things, Hv23t decided to do some tinkering to see what could be done with them.

He started with modifying one of the electric hot water heater tanks he got. It was first checked for any leaks, and then he went about installing a coil of 30 foot long 1/4″ copper refrigerant tubing into the tank through one of the heating coil holes. This is similar to what the A7 AirTap does. To seal the tubing entrance/exit points, he reused one of the hex plugs in the tank. It was drilled and tapped for 1/8″ npt fittings. He then inserted 1/8″ npt to 1/4″ compression fittings in the two holes. The 1/4″ tubing was fed through the compression fittings and the hex plug was re-installed in the water heater tank.

The next step was to get one of the dehumidifiers working. Hv23t found that one of the dehumidifiers had hardly any R22 refrigerant left in it, so he pumped some more refrigerant into it and it came right back to life.

Not happy with that setup, he used a vacuum pump to remove the R22, and instead filled it up with propane. To do this, Hv23t modified a propane torch tip by brazing a 1/4″ flare fitting to the end of it.

The new setup using propane (R290) reduced power usage from 435 – 450 watts down to 365 – 410 watts. He also measured the temperatures in the 140s (F) on the hot side. Sounds plenty warm for hot water.

With the dehumidifier now working and even having its inefficiency increased, it was time to hook the dehumidifier up to the hot water tank and do a little modification to the dehumidifier as well. The 1/4″ tubing from the tank was brazed to the hot side of the dehumidifier’s heat pump. At the same time, the existing heat exchanger from the hot side was replumbed into the cold side increasing the cold side heat exchanger’s surface area.

After everything was replumbed, the water heater was ready for its first test. The tank started at 67 degrees F (19.5 C) and after 1 hour and 51 minutes the heat pump kicked off at the hot water heater’s set point of 100F (38C).

The test was a great success, but of course there were some issues to fix up. The biggest one being that the cold side heat exchanger frosted up like a brick of ice. This significantly hinders its ability to exchange heat which reduces efficiency. We’ll look at that issue, the installation and efficiency testing of the heater in the next article.

For more details on this project, see Hv23t’s forum thread.

In our first article, I explained my needs/wants for the alarm clock and ended up selecting the Elgin 3350E shown above. It is a battery powered alarm clock with an automatic back lighting feature. If the room is lit up by the sun or by lights, the clock turns the back lighting off to save on battery life. However, once it gets dark in the room, it turns the back light on so you can see what time it is. It also has some pretty good reviews on amazon and it is also pretty inexpensive.

The clock requires 3 AA batteries. The batteries I will be using are what you see above. They are some nimh rechargeable batteries I nabbed from the local harbor freight. Any nimh battery will work, but you may have to change what solar panel you use according to what batteries you have to use in the clock.

Now that we know what batteries we’re going to use, we can figure out how to charge them. I did a bit of surfing to find some good info and came across this site:

How to charge nickle metal hydride batteries

“The cheapest way to charge a nickel metal hydride battery is to charge at C/10 or below (10% of the rated capacity per hour). So a 100 mAH battery would be charged at 10 mA for 15 hours. This method does not require an end-of-charge sensor and ensures a full charge. Modern cells have an oxygen recycling catalyst which prevents damage to the battery on overcharge, but this recycling cannot keep up if the charge rate is over C/10. The minimum voltage you need to get a full charge varies with temperature–at least 1.41 volts per cell at 20 degrees C. Even though continued charging at C/10 does not cause venting, it does warm the battery slightly.”

This is a great bit of info for us. It contains basically everything we need to figure out our solar setup. Prepare yourself for a little math and electronics speak as we delve into the world of charging batteries.

The batteries I am using are rated at 2200 mAh. The quote above says I can charge them at C/10 safely. C is the battery capacity which is 2200 mAh. This simply means that I can charge them at a rate of 2200/10 = 220 mA. So, I want to find a solar panel that puts out 220 mA or less to avoid doing any damage to my batteries. This is great news because it means I don’t need a charge controller or any additional circuitry to complicate things.

The next step is figuring out the solar panel voltage. Again, we’ll look at the quoted paragraph that says we need at least 1.41V per cell. Well, the clock is using 3 batteries, so we need to provide 3 x 1.41V = 4.23V. Unfortunately, you can’t just go out and buy a 4.23V solar panel. However, 5V and 6V panels are readily available. Either of these will work, but we have to figure out a way to get them to put out 4.23V.

I ended up purchasing the solar panel you see above from ebay. It is rated at 5V output and 200 ma. A 6V panel that is rated for 220 ma or less would work just fine too.

But, we still have to get the panel’s voltage down to 4.23V. To get this voltage drop is actually quite easy, and it is going to be done by another component we need for the solar setup anyway. That component is a diode. It is essentially a one way / check valve for electronics. The diode is not only going to provide a voltage drop down to 4.23V, but it also stops the solar panel from draining the batteries when the sun isn’t shining on them. All solar panel setups use these, and you can get them with different voltage drops.

To get the diode, I went to digikey.com. They have an insane amount of electrical components and shipping is pretty cheap too. This is the diode I selected if you want to use a 5V panel like me. It will provide an approximate voltage drop of .75V giving an output of 4.25V which is close enough for this application. Alternativly, if you wanted to use a 6V panel, this diode should work fine for you. It has a 1.75V drop and will give you a similar 4.25V output.

Once I get all these things in the mail we’ll start putting them together!

For the latest info and a bit more detail, see the forum thread.

I am in the market for a new alarm clock. My old one I’ve had for around 10 years now and it has recently started making an annoying electric buzzing noise similar to a bad florescent light. I also know that it pulls a constant 3W from the wall according to my killawatt. This seems a bit ridiculous considering there are plenty of alarm clocks out there that run for long lengths of time on a single AAA battery. Anyway, I figured it would be cool idea to get an alarm clock that was solar powered. I don’t need fancy features like a cd player or even a radio that the old alarm clock had (and I never used). I just need something I can see in the dark, and something that will wake me up.

I started by doing some googling and amazoning, but wasn’t really able to find what I was looking for. All of the solar powered alarm clocks I found don’t have a back light that is on all night long, probably to increase battery life. My alarm clock is set out of reach, so a ‘push to light up button’ isn’t going to work for me. So, my search for an off the shelf solar powered alarm clock quickly came to an end.

What is a guy to do if he can’t find a product that fits his needs/wants? Well, if you’ve read EcoRenovator at all before (or if you read the title) you already know the answer, DIY!

What I did instead was started searching for some battery powered alarm clocks with the features I wanted. You can always add a solar charging circuit to something that has a rechargable battery in it. What I found was that there are a few alarm clocks out there that do have back lights that stay on all night, but turn off if there is light in the room. This was a nifty power saving feature that helped narrow down my selection. In the end, I selected the Elgin 3350E. Its even quite reasonably priced. I chose this clock over my second choice because it uses 3 AA batteries versus 3 AAA batteries and I’m betting that the AAs will last longer. However, the larger batteries also do give us another advantage that I’ll talk about in the next article when we figure out the second half of this setup, the solar panel charging.

Check out the next article in this series, DIY Solar Powered Alarm Clock – Solar Panel Charger.

If you’d like to see the latest news on the DIY solar powered alarm clock just hit the link to our forum.

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.

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.