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Is it on, off, or idling and how to tell

February 17, 2010

I’m sure most of you have heard or read that some appliances still use electricity when they’re “off.” There is no doubt this is true, but how can you tell? Identifying what’s idling and what isn’t (without paying money for something like a Kill A Watt Monitor) is a good first step.

How much energy is really being wasted?

Measuring the ethernet router’s power supply An idling appliance is something that uses electricity when it’s “off.” When “off,” they could use anywhere from about 5 to 25 watts. Usually these appliances have internal clocks or settings. Unplug the appliance if you don’t care to keep time or settings you may have saved.

A disconnected cell phone charger, laptop power supply, or any external power supply not connected doesn’t need to be plugged in. Depending on how they work, they could use anywhere from 0 to 10 or more watts.

Here are the results (in watts) of some measurements I took:
  • Nokia cell phone charger (not connected):
    0W
  • Laptop power supply (not connected):
    2.5W
  • Ethernet router power supply (not connected):
    8.9W
  • Cassette deck, “standby” (it’s not labeled “off”):
    2.5W
  • VCR/DVD player, no clock, completely “off”:
    5W
  • Older PlayStation 2 turned “off” from the front button:
    6.3W
  • Older PlayStation 2 turned off from the back switch:
    0W
  • Computer, completely “off”:
    10W
  • Older VCR with clock, completely “off”:
    13W
  • A Sony stereo system with disc changer, cassette deck, and clock, completely “off”:
    25W

How can I tell if something is idling?

Common Indicators:

  • Lights or a display is still on and working
  • It hums or makes any noise when you put your ear right up to it
  • It can automatically turn itself on (as through a timing function) if it’s “off”
  • It is warm to the touch due to power dissipation

Typical Appliances that Idle when “Off”:

  • Desktop computers made after 1995 (or after ATX was introduced)
  • Laptops
  • Computer monitors and TVs
  • VCR/DVD/Blu-ray players
  • PlayStation, Xbox, Nintendo, and other gaming systems
  • Satellite receivers
  • Cell phone chargers
  • Answering machines
  • Anything that has an external power supply
  • Anything that keeps time

Push-Button Switches

Another way to tell if an appliance is idling is by the power button or switch. If the power button is small and requires a gentle push with a subtle “click” or “tap” sound, it likely idles.

If the power button feels heavy duty, making a “click-cling” or a “click-clack” sound, it probably doesn’t idle. This is because these switches usually switch the wires straight from the power cord. It’s the equivalent to unplugging it. This is common in much older appliances, especially stereos and amplifiers.

Toggle Switches

If you have an appliance that has a toggle or flip switch like a power strip, it probably doesn’t idle. However, if the switch is small, thin, or light, it might use idle power.

Too Much Hype?

Another point I want to get across is don’t be too optimistic. Most idling appliances use very little electricity. Also, new power supply designs continue to increase in efficiency during idle time. Consider that a laptop or cell phone also uses idle electricity when it’s completely “off” (unless you have no battery).

Air conditioners and heaters make the meat of your electric bill, not idle power or lighting. Unplugging any one appliance will probably make a negligible difference. It’s when you have several that they have an impact.

Turning off a power strip to everything you’re not using is a good idea. Even the Smart Strip uses some idle power. If you’re still using any incandescent light bulbs, you’ve got a slightly bigger problem than idle power.


Choosing solar panels

February 16, 2010

There’s a lot of different solar panels out there, and with so many choices, it would be helpful to know what to look for when buying one. I’m going to explain some of that technical jargon. This way you can better understand how or what panels to use with a given system.

Understanding the Spec./Data Sheet

Let’s say you want to check out a specifications sheet for a solar panel, like this one or this one. As you start looking at the tables, you’ll see terms like:
  • Polycrystalline silicon (or Multi-crystalline silicon)
  • Monocrystalline silicon
  • Open Circuit Voltage (Voc)
  • Maximum Power Voltage (Vpm) (or Optimum Operating Voltage)
  • Short Circuit Current (Isc)
  • Maximum Power Current (Ipm) (or Optimum Operating Current)
If you’re viewing a solar panel product page and can’t find Voc, Vpm, Isc, and Ipm, you should be suspicious!

(As we discuss these terms, keep in mind that voltage and current measurements are usually taken under a consistent test light source. The results should be comparable to good sunlight.)

Vpm and Ipm

These are the most important aspects of the solar panel because they determine power. Both Vpm and Ipm are the ideal maximums at which the solar panel functions. Looking at Ohm’s Law, we know that:
  • Vpm * Ipm = Power (Watts)
If you multiply Vpm and Ipm and don’t get something close to the advertised wattage, you should be suspicious.

This may seem trivial and basic for some of you, but the point is that you need to know what is being advertized. What is a “12 volt” solar panel? Is it 12 Voc with about 9 Vpm? Or is it 12 Vpm with 18 Voc? I admit, it’s usually the latter, but you need to make sure.

MPPT - Maximum Power Point Tracking

Both Vpm and Ipm establish the maximum power point. When you see a charge controller or grid tie inverter, they may advertise a MPPT (maximum power point tracking) feature. All this means is it searches for Vpm and Ipm to get the most power from your solar panel(s).

Voc and Isc

Consider Voc and Isc as the opposite extremes of Vpm and Ipm. Generally, you don’t really need to worry about these. You won’t get any power output at these extremes.

Open circuit voltage, or Voc is the voltage measured when the panel isn’t connected, hence “open circuit.” Short Circuit Current, or Isc is the current (amps) measured when the panel is completely shorted, positive to negative.

Poly-crystalline vs. Mono-crystalline Silicon

This makes up the composition of the silicon used in the solar cells of a panel. Silicon is the same material that make up computer chips. You don’t really need to worry about the raw materials that make up a solar panel. But for your interest, here are some key differences:

Composition Cost Efficiency Appearance
Poly-crystalline less less usually rectangular or square without rounded corners
Mono-crystalline slightly more slightly more usually square with rounded corners



Buying a simple grid-tie solar system

February 12, 2010

If you’ve done any amount of home improvement, then setting up a simple solar system isn’t a challenge. However, it would be good to know a few basics and what parts you need.

Please keep in mind you may have to contact your power company to learn specific code requirements. Where I live, our house wasn’t required to be wired to code; therefore I simply discuss what will work from a technical standpoint.

Jump in Head First

If you want to jump right in and buy a simple low cost package that outlines all the details, here they are:
There are probably more out there, but this remains constant for a simple low cost package: small inverter, few (or one) solar panels. Note in particular the micro inverter, which I will discuss details in another article.

How These Systems Work

These systems are very simple. Think of it as battery charger working in reverse, except the battery is the solar panel. A solar panel is connected to the inverter, which is connected to your breaker box. The inverter is “charging” your house using the solar panel “battery.”

If you’re familiar with inverters used in cars for laptops, they are very similar. However, there is a serious difference between a grid tie inverter, and a basic inverter. A grid tie inverter synchronizes with the frequency (60Hz) and phase of the voltage from the power company. (Think of it as two people flipping a switch at the same time, in the same direction.)

Buying Parts Separately

The essential parts you need for a simple grid tie system is a solar panel and an inverter. You need to consider both items at once for a complete working system.

Inverter

The inverter is what converts the input VDC (voltage, direct current) from the solar panel to the output VAC (voltage, alternating current) to your home. You need to consider voltage, both input and output. This will determine the voltage of your solar panel and how to connect it in your breaker box.

Good inverters can work with a range of voltage input, like 10-30 volts DC or 40-60 volts DC. Output voltage is usually ~120VAC, ~240VAC, or ~208VAC. You need not worry about the last one, it’s for commercial three phase power systems. Check out my article Is solar power really affordable? for additional information.

Power Source

Solar panels come in lots of flavors and output voltages vary widely. (See my article about choosing solar panels for details.) Here’s a list with some common voltages according to open circuit voltage (Voc) and optimum operating voltage (Vmp):
  • ~18Voc (12Vmp)
  • ~36Voc (28Vmp)
  • ~58Voc (47Vmp)
Alternately, you could use a wind generator. Typical voltages are:
  • 12V
  • 24V
  • 48V

Hardware

As for mounting hardware, you could use angle iron or angle aluminum usually available at a local hardware store, Lowe’s, or Home Depot. Wood or angle brackets are other options, but I recommend against duct tape.

If you go with a wind generator, tower kits are usually sold separately. You may also have to buy galvanized steel pipe for a guy-wire tower kit. See some examples here.

Putting Everything Together

After you’ve got the parts, all there is left to do is wire it and mount it. With such a simple system, all you have to do is connect the solar panel to the inverter. Afterward, you connect the inverter to your breaker box or just plug it in a standard household outlet. I’ll discuss wiring details in another article.


Understanding plug-in hybrids

February 11, 2010

Plug-in hybrid electric vehicles (PHEVs) are coming, and fast, but how do you find the good ones and what makes them so different from traditional hybrids? The answer lies in the proportion of gas vs. electricity.

Getting best bang for your buck

If you’re looking to get the most bang for your buck, try to find a PHEV where the electric motor does all or most the driving. It should be able to reach 55 mph or greater without help from the combustion engine. Also try to make sure the range is at least 40 miles, or your normal commute. Otherwise, the plug-in feature will be much less meaningful.

Unfortunately, most of these features will probably only come in a series hybrid. I recommend BYD’s (Build Your Dreams) F3DM.

In a true series hybrid, the electric motor does all the work. A typical (parallel) hybrid uses the engine and electric motor side by side. As a result, you’ll be using both gas and electricity.

Series Plug-in Hybrids

It is the series hybrids that can greatly reduce, if not eliminate, gas needs. This is because the engine is simply an extension of an electric vehicle (EV).

In a true series hybrid, only the electric motor drives the vehicle. The engine generates electricity for the battery and electric motor, like a standby generator. You shouldn’t use any gas if you don’t travel far. It doesn’t matter how fast you go. It’s an extended range EV.

What’s Available?

BYD’s F3DM and GM’s Chevrolet Volt are examples of series hybrids. Besides these, there doesn’t seem to be any true series PHEVs available that don’t use the engine for higher speeds.

The BYD F3DM can work as a series-only hybrid OR a parallel hybrid. Hence the “DM” indicating the dual mode ability of their new F3 model. The Volt is a true series hybrid as far as I know, but it’s also an expensive luxury car.

Typical Plug-in Hybrids

Most up coming plug-in hybrids will be like an extension of a parallel hybrid, like the Toyota Prius. They’ll have a slightly larger battery and electric motor. These hybrids can reduce your gas needs, but not eliminate them. Check out a list on Eartheasy.

A good PHEV should closely resemble a series hybrid. This is why the battery is larger. You plug in your vehicle and let it charge. You don’t plug in a traditional hybrid because the battery is tiny.

Typical Parallel Hybrids

Traditional hybrids use a system of combined electric and gas power, but unequally. The electric motor is typically used for easy acceleration and coasting in low speed city roads. It’s the engine that does most of the work on the open highway. That’s because the battery and electric motor are small.

If you drive faster than about 30 mph, the engine takes over. Once it does, it will start charging the battery and driving the vehicle. It can save on gas, but not as much.

The focus of older hybrids was to make gas vehicles more efficient. The focus for PHEVs should be to give electric vehicles a longer range using gas. If you buy a PHEV, try to make sure its electric motor attributes outweigh its combustion engine attributes.


Is solar power really affordable?

February 1, 2010

Solar power is affordable… when you consider the result and what solar “power” actually means. Most people think of massive solar panel arrays costing thousands. But solar power is about using the sun to your advantage. You could do this several different ways:
  • electric solar panels
  • solar water heating
  • solar lighting
  • solar heating (opening window blinds)
  • growing vegetables
  • and more

Electric (PV) Solar Panels

A Solar Cell Let’s look at electric solar panels, or photovoltaic solar panels (PV). When buying solar panels, (or inverters), you need to consider dollars per watt ($/Watt). Around $2.50/Watt is a good price for solar panels and $1.00/Watt for inverters.

You don’t have to buy several panels at once like yesteryear, but it’s usually cheaper to buy a panel with many solar cells. (I recommend eBay for panels.) Don’t forget about government incentives.

To sell power back to the electric company, you’ll need a grid tie or grid interactive inverter. Here are some options according to power:

Solar Water Heating

Solar water heating saves your water heater from doing all the work. A lot of energy is required to heat water. Costs for solar water heating systems can range from $1000+.

If you live far south, you may be able to use a passive system (without pumps). But most systems use pumps to circulate water through a solar collector.

Solar water heating arrangements seem to vary much more than electric (PV) solar panels. If you’re considering solar water heating, I’d recommend reviewing details on these helpful pages:

Solar Lighting and Heating

Simply open the blinds of a window. This is very helpful during the winter since heat also comes through a window. The more windows you have on the south side, the warmer winter can be. It costs $0 and can lower your heating bill. Now that’s free energy!

Skylights are another common option, but usually need to be considered before construction. However, a strategically placed mirror may also get the job done.

Growing Vegetables and More

If you grow your own vegetables, you don’t have to buy as many. However, some gardening experience would be helpful.

Don’t think these are the only ways of using the sun to your advantage. Look for other ways of using the sun, like the classic solar oven.