Short Days and Warm Showers

If you’ve been following my blog, you know I use solar to heat the water I use in my home for washing and bathing. It takes about 3 hours of good sun each day to keep up with all of my hot water needs. When we get a few clear days, the water storage gets hot enough that I can go a couple days with heavy overcast conditions.

This time of year, the sun is only effective for heating from about 09:00 AM until about 3:00PM. That’s not a big window, if the day is partly or mostly cloudy. Furthermore, we seem to get a couple of sunny days, followed by 3 or 4 cloudy days. I gave in and turned on my electric water heater for one day in late December. Otherwise, there are days when I have to take a warm shower, instead of a steamy hot one.

For me, this has sort of become a crusade; to try to get by on what the sun provides. It’s not much of a sacrifice. Most of the year, I have more hot water than I can use. However, these short days, combined with overcast conditions, really do test my resolve. Occasionally, in the summer, we get a week of rainy dark weather and I run out of hot water, but it hardly matters, because I take some of my showers outside in the summer, anyway. Hot showers just aren’t as important to me when it’s 90 degrees Fahrenheit (32C).

I just purchased another photovoltaic panel and a new charge controller so I can add about 300 watts of capacity to my solar electric system. It also suffers a bit when the days are short and overcast. I have batteries to get me through the dark times, but they need time to recharge at least twice a week. I hate to add more batteries, because they have a relatively short lifespan (see my other blog entries on battery woes). I don’t need more photovoltaic capacity in the summer, but I definitely need it in winter. I’ll figure out some way to use the excess power in the summer. I’ve been working up some ideas for a while. One of those ideas is to power the refrigerator off the solar during the day, and let it switch back to the grid at night. That would let me use more energy while the panels are generating it, and not put an additional load on my batteries.

I took the Polar Bear Plunge on January 1st. It’s the 2nd time I’ve done it in North Carolina. It was a good time. The water was 49 degrees Fahrenheit (10C) and the air was about the same. The sun was shining and it wasn’t windy, so it was really a nice day, considering it was January 1st.

Do the Math premiere

You can (and should) view the “Do the Math” movie on-line on YouTube. The movie was produced by The movie is a call to action to stop or substantially reduce carbon emissions before our planet warms more than 2 degrees Celsius above pre-industrial levels.

On a lighter note, solar panels (photovoltaics) can now be purchased for under $1/watt with a 25 year warranty. That is a pretty good deal, even without government subsidies. I have never filed for tax rebates, as a matter of principle. But, I digress …

I’ve been looking into adding a wind turbine to my energy production. The turbines that sell for under $1000 do not impress me. They have small blades and only produce any real power in high winds (25 mph+). It is getting windier, where I live, but a turbine that could harness a 15 mph wind would serve me much better. I’m looking at building a turbine, specifically designed for lower wind speeds. I’m also thinking of purchasing some additional solar panels. At $1/watt, I can’t go wrong. The catch is that my charge controller would need to be replaced, and I might have to add some batteries.

I just got a letter from my electric utility. Electric rates are going up 5% in May, and the facilities charge (a fixed monthly fee) is also going up. I’ve been debating a grid tied inverter, so I could make better use of my photovoltaic output. As it is now, I have excess capacity most afternoons; especially on sunny days. With the increase is the monthly connection fee, I’m tempted to invest my money in going off grid, completely. Going off grid is an attractive idea, but the ramifications of going off grid are nothing to sneeze at. I would have to be able to provide for peak demand, and I’d have to have backup power for when the sun didn’t shine and the wind didn’t blow. For now, that is just not an option. For now, the goal will be to get the electric bill as low as possible.

On an unrelated note, I found time to rebuild my robot car. It’s been fun, writing the software for autonomous navigation. I’ll have to return to my robo-car in a future blog entry. That’s a lot more fun than talking about the destruction of our planet.

The little things

I’ve been really busy these past couple of weeks with work. Last weekend the weather was dark and rainy. Today, however, the sky was blue and the sun was shining all day. I took full advantage of the sun’s bounty. I did laundry and hung my clothes out to dry on the clothes line. I baked bread in my SunOven, and I warmed my house with passive solar and a solar air heater. Of course, all of the hot water I use is solar heated.

The solar thermal systems are by far the most cost effective. You may not think of a clothes line as a solar powered appliance, but it really is. Reducing your carbon footprint doesn’t have to be expensive, or technically daunting. My solar oven from is a very simple device, and it works great, as long as you can do your cooking while the sun is shining. Food cooked in the SunOven even tastes better, for some inexplicable reason.

My motivation for writing this came from a story I heard on the radio. I feel very fortunate in that I have the resources to take advantage of renewable energy. I realize that some people just can’t afford to invest in renewables, even though it would probably save them money in the long term. Actually, the best reason for a person with limited income to reduce their dependence on the grid, is that it saves money and offers some peace of mind, knowing that if the power gets shut off, you’ll still have some basic needs covered. It’s also a lot easier to pay those energy bills when they are a whole lot smaller. From a “save the planet” perspective, people who live modest lifestyles are not the biggest concern. Large office buildings offer a much more significant target for real carbon reductions. People who live in 6000 square foot homes, could obviously convert those into apartment buildings and move into something more practical. However, I doubt any of those people are reading my blog.

Based on my experience with energy conservation, there are several things you can do to get started saving some of your hard earned cash without investing anything. You may already be doing some or all of these things, but they are worth mentioning.

1) if you drive, plan and consolidate your trips so you drive less.

2) turn down your thermostat, don’t leave the frig door open, turn off lights, etc., etc. You’ve probably heard most of those tips 99 times.

3) if you don’t use a lot of hot water, you can turn your water heater thermostat down to 120 and save some power.

4) use a clothes line instead of the clothes dryer whenever you can. It may be inconvenient, but if you do it often, you’ll save some real money.

5) water can only get so hot before it turns to steam. If you’re cooking something in boiling water, lower the heat to where it will just barely keep boiling. Put a lid on it, if you can. There are some things that call for a rolling boil, but in my experience, most things cook the same whether the water is boiling fast or slow.

6) turn off your TV when nobody is watching it. Actually, you’d be doing yourself a favor if you left it off most of the time.

7) put your computer to sleep and/or turn off the monitor when it’s not in use during the day. Shut it down at night.

Those things won’t cost you a dime, but they could save you a bundle. If you can make a modest investment, replacing tungsten bulbs with more efficient bulbs will pay off in a year or two, depending on how much you burn your lights, and the bulbs you buy. I have a couple of 7.5W LED bulbs in my kitchen that were an experimental purchase. I’m sure they’ve saved some energy. My kitchen light is the one that is on from the time it gets dark until I go to bed. It is where I spend most of my time when I’m in the house and I’m not working or sleeping. I wish I could say that the LED lights are performing flawlessly. They are probably about 1 year old and one of them has taken to flickering. An LED can last for 100,000 hours of use, but they run on low voltage DC current, so an LED version of an AC bulb (one you’d screw into a standard socket in your home) requires some electronics to convert the AC high voltage power into low voltage DC current. Apparently my bulb is defective, or it was cheaply made. I may bust it open and see if I can repair it. However, the 12V LEDs I’ve been experimenting with will likely replace my ceiling lights. I will have to run wires around the house to connect them to the battery bank that is charged by my solar panels, but once I do that, I’ll have bright, cheery, low voltage lighting that is also highly efficient and will be there for me, even in a power outage.

You might think I’m rich, but I’m not. I live on a very modest income that is well under half the national average. I use the money I save on my energy bills to buy parts, I salvage and fabricate whatever I can, and I do all of the work myself. I do spend money on my solar projects. Of that, there can be no doubt. My recent battery purchase was $400, and I’m afraid those batteries may not pay for themselves before they need to be replaced.

The fastest payback with solar electric systems is to use a grid-tie system where you don’t store anything. You use the energy you generate while you’re generating it. If you generate more than you can use, your electric meter runs backwards, and when the sun goes down, you rely on the grid for your power needs. The problem with that system is that, when the grid goes down, so does your solar production. You have all that potential, but you cannot use it when you need it most.

I’m more of a boyscout than I am a shrewd business person. I want my solar power to provide me with some security against outages. My solar panels charge a bank of batteries and power some nominal loads during the day. At night, I run some lights and computer equipment off the batteries. You lose 20-30 percent of your power when charging batteries, and when the batteries are fully charged, the potential of my solar panels is often underutilized. The advantage is that my system is completely independent of the grid. It’s like a giant uninterruptable power supply (UPS).

Since I have admitted that I’m not the shrewdest business person, I might as well mention that I have taken no tax credits on my investments. I don’t need the government to subsidize my choices. There are some pretty lucrative tax credits to be had, and I don’t blame anyone for taking advantage of them. That is just not my way.

Hurricane Sandy may have been the storm of the century, but there are going to be more like it in the next 5 years. Of that, I am pretty sure. People should be talking to their neighbors about how they’re going to weather the next big storm. A distributed power generation system is much more reliable than a centralized one that relies on miles of wires to deliver power. At least me and my neighbors will have a place to charge their cell phones. It’s too bad all the cell towers will probably go down.

LED lighting

LED Light from the frontI’ve been experimenting with these LED arrays by Bridgelux (Mfgr part #BXRA-C1202-00E00, Digikey part #976-1005-ND*). They are rated at 2 Amps max current, but so far, I am not driving them anywhere near their rated power. In the tests shown here, the LEDs installed in my homemade lamp are drawing 22 watts of power; combined. They’re 2 Amp rating with a 12.8V forward drop would equate to 25.6 watts per array, so I’m powering the 4 arrays at about 25% of their capacity. The reason for that is convenience only. I intend to bump the power supply voltage when I get a chance to build and test a constant current power supply.

In spite of the efficiency of LEDs, they still produce too much heat to operate without a heat sink. In these next photos, you can see that I have each LED array mounted on it’s own heat sink. The heat sinks I used were salvaged from old computers. They are CPU heat sinks, and they are overkill for what I’m doing, but they were in my junk box and they do the job.

LED light from the side LED light from the back

Just to give you a frame of reference for how much light these LEDs kick out, with only 22W of power, I took some photos with fixed camera settings (except I used tungsten white balance with the tungsten bulb and daylight white balance with the LED light, because the LED light temperature is much cooler than the tungsten light. i.e. the LED light is closer to daylight in color balance). So, the next two photos are brightness tests. The one on the left is the 100 watt tungsten, and the one on the right is the 4 LED arrays operating at 25% power, and consuming a total of 22 watts.

Photo with 100W tungsten light Photo with LED light

You may notice that the tungsten light bulb produces a single, fairly soft shadow. The 4 LED arrays produce several shadows, and the light is much whiter. It is also worth bearing in mind that I can get this much light from a single LED array, when it is powered at it’s full rated power.

Right now, I’m working on building lights for shooting video. I am certain that my LED lights will eventually replace my 650W halogens, and I’ll be able to power them from batteries. Obviously, they will produce much less heat and use less energy, but also, the LEDs should last a very long time and they are very durable, unlike halogen bulbs. It will probably take 6 LED arrays to generate as much light as a 650W halogen, but it would be easy to install 6 LED arrays in a single light fixture, and, given their longevity, they will pay for themselves in bulb replacements, if not in energy savings.

Of course, all of this experimentation is going to come home. I plan to wire my house for low voltage LED lighting with motion controllers that will turn the lights on where you need them and dim them where you don’t. I don’t think I’ll be using these high powered LED arrays in the house. Maybe I’ll use one or two in the kitchen. I envision a more distributed lighting arrangement with many smaller LED lights installed all over the ceiling for very even lighting. No matter how I do it, I can expect to use less than 1/2 the energy that my compact florescent bulbs use, and I’ll never have to replace another bulb. Furthermore, I like the idea of using 24VDC for the lighting because my solar panels produce DC power. By eliminating the conversion to 120VAC, I’ll get another efficiency boost. I can easily illuminate my entire house, using LED lights and power from my photovoltaics (solar electric panels).

* If you decide to purchase one or more of these LED arrays, be sure to purchase as many LED array holders (Digikey part# WM4556-ND) with them, because they are nearly impossible to wire without the holder. With the holder, they are a breeze to wire. The holder is manufactured by Molex, Inc. and the Molex part number is 1801500000. The LED arrays can be powered directly from a 12V battery with no current limiting resistor, but they will draw only around 0.6 amps at 12.5V. They still put out a lot of light at 0.6 amps, and it may be worth operating them like that, just for the pure simplicity of wiring. There are many variations of these arrays with different color temperatures, different power ratings and various forward voltage drops. If you want to go with 12V power, you might try something with a forward voltage drop of 12.5V or 12V. Be careful, though. It’s pretty easy to fry an LED if you let too much current flow through them.

A Word About Life

A recent life experience has prompted me to write this …

If you run off the people who care enough to tell you things you don’t want to hear, your world view will be shaped by lies and half-truths.

I may not be happy to hear what you have to say, but that doesn’t mean I don’t want you to say it. I strive to make solid decisions, based on all of the available information. My capacity for observation is limited. I’m one of those people who tends to think out loud, at times. I do that because I want others to critique my thought process. It is nearly impossible to critique one’s own thinking. I don’t want to go blissfully into self-serving banality.

Speaking of decision making, I think I’ve finally decided to go ahead with the lead acid golf cart batteries for my solar power storage. They have a pretty decent life span and they stand up well. I have a little money in the budget, so I guess I’ll be purchasing those pretty soon. Once I have more battery capacity, I can connect more loads to my solar power system and make better use of the PV capacity.

I was pretty happy with my summer energy usage. Between the steel roof, the solar water heater, limited use of my photovoltaics, and the sun oven, I managed to cut my power usage by 40%. The goal is not to get off the grid, but to become somewhat energy independent; in the event of a long term outage, and to insulate myself from increasing energy costs, without going into debt. I am making progress towards that goal, but I have to stay within my budget. It’s a slow process.

It is noteworthy to add that I don’t expect all of these systems to pay for themselves in the short term (under 10 years), although some of them already have. The PVs may never pay for themselves, but I hope they pay for the batteries. This is all part of my retirement plan. I’m making investments today that will continue to pay dividends, long into the future.

Which brings me back to how this entry started. Good friends are also investments, and pseudo-friends are liabilities. I suggest that everyone should hold on to the people who help them grow and improve. Whether or not you keep the others around is just a cost/benefit equation. I think I know who my real friends are, and that’s where I make my real investments.

Life is hard, but it could be worse! 🙂

Liquid Metal Batteries

Speaking of batteries, I wanted to post this link to some very promising new technology that could revolutionize the use of renewable energy and eliminate the need for “backup” generators. The video is fairly long, but the professor has a great sense of humor and I found the presentation both interesting and uplifting.

Check it out: Grid Scale Metal Liquid Batteries


Batteries are the bane of any off-grid renewable energy system. Whether you use wind or solar to provide the power, you must have a way to store some power for when the wind stops blowing or the sun goes down. You also need surge capacity for powering loads that require a lot of amps for a short time. Aside from the heuristics involved in figuring out exactly how much storage capacity you’re going to need, you’ve got various types of batteries, different levels of quality, etc. The cost of batteries eats up 1/2 of the value of the power I can generate. The alternative is to use a grid connected system, but that doesn’t provide any power when the grid goes down! I use my PV system like a huge uninterruptable power supply. I power some of my equipment with it, and, when the grid goes down, it is my backup power.

Up until now, I’ve been using deep-cycle, flooded lead acid batteries. They are powerful and relatively inexpensive. My current battery bank is about 220Ah, of which I can use about 110Ah without over discharging the batteries and shortening their life. I really need a larger bank to take advantage of the power I can generate with the photovoltaic (PV) panels that I have and to get through days with no sun. My panels and my charge controller are capable of a 30A charge rate (approximately). With flooded lead acid batteries, I should get about an 85% efficiency in charging, and I can bulk charge the batteries at the full rate up to 80%. So, after a long night of a nominal 10A draw, I can bulk charge at 20A (30A PV subtract 10A nominal load) for about 4 hours before the charge rate drops and PV power is wasted as the batteries are charged from 80 to 100% charge. That means my battery bank is too small.

With a larger battery bank, I can bulk charge for longer, and I can increase my nominal load. i.e. I can utilize more energy and make better use of my investment. So, I’m researching my options for a set of batteries with at least a 400Ah capacity. I am looking at 2 options, at the moment …

Option 1:

Flooded lead acid batteries, 6V, 220Ah x 4 with an assumed 85% charge efficiency and a 5 year life span (440Ah @ 12V).

If I replace 200Ah of charge each day @ 20A, that would require 10.5 hours of direct sunlight (@ 85% efficiency), so the bank should be large enough.

(cost $360 or $72/year)

Option 2:

Absorbed Glass Mat (AGM) lead acid batteries, 6V, 190Ah x 4 with an assumed 95% charge efficiency and similar lifespan (380Ah @ 12V).

I can only use about 190Ah from this bank, and the batteries recharge more efficiently, so it would take about 10 hours of full sun to recharge this bank.

(cost $560 or $112/year)

It really looks to me that the AGM batteries are just going to cost me $200 more and provide little additional benefit. A flooded lead acid battery can be bulk charged up to 25% of it’s Ah rating. Option 1 could be charged at 110A, but the most I can throw at it (at the moment) is 30A. The down side is that I lose more power to heat with the flooded cell battery than with the AGM version. That would be a big deal, but for $200, I could add an additional 85W of PV capacity, which would more than make up for the 15% loss and the new PV panel would last for 20 years (at least), which comes to $10/year, whereas the additional battery cost comes to $40/year (assuming the price of batteries doesn’t go up).

So, I guess I made up my mind. I’m going to go with the cheaper, less efficient alternative, unless someone can offer some helpful advice or show me the error in my logic.