Earth Hour

March 28, 2008


Calling Every Citizen


The Planet Earth


You are asked to show you concern for the Earth’s Environment by turning off every light AND everything electrical that is not essential, for just one hour on Saturday March 29th at 8pm your local time.
This idea was started by World Wildlife Fund in Australia last year, has been spreading rapidly throughout the world. The purpose is to raise awareness of Global Warming and the Energy Crisis.
Please e-mail and text as many people as you can about this effective and worthy idea. This is a real demonstration of the power of the people, or if you like; THE POWER OF ONE. It can make a huge difference if enough people participate.

ESB to half emission by 2020, be zero carbon by 2035

March 28, 2008

ESB, the irish Electricity board, plan to spend 22 Billion over the next 12 years to half the carbon footprint of the grid. That is pretty excellent in my book. I hope you all agree. 

Even more challenging is to be zero carbon by 2035. So for those of you thinking about getting into the Energy Business… the future looks bright!

Understanding Solar Panels 2 – Solar Photovoltaic

March 26, 2008

A solar PV system is a system that directly converts the suns light into electrical energy. This electricity can then be fed into the electrical system of the house, office or factory where it can be used on it’s own, or in conjunction with the main electrical supply. Solar PV can therefore directly reduce or remove the electrical costs of the user. In some cases electricity can even be exported by larger solar PV systems onto the electricity grid, providing a source of income.

The science bit
The PV panels are positioned so that maximum light will shine upon them over the course of the day. Light which hits the panel, passes directly through the glass plate, found on the surface of the panel, and into the silicon layer of the panel. The energy from the light excites electrons within the silicon semiconductor layer of the panel, creating an electrical current. This current is then passed through a piece of electrical switch gear called an inverter, before going on to the main fuse board. The inverter converts the current from DC (like in a battery) to AC (like in a house). From this point the electricity supply the needs of the building. If the demand is too great, electricity from the main electricity supply can combine with it to provide for the demand. If it is too little the electricity can charge a battery, or be fed onto the national grid. As there is no sun light at night, a large battery would be required to keep a supply over the course of the night.

Solar PV

So… Do they work?
In comparison to other renewable technologies, solar PV panels are relatively immature. Most experts believe that PV would be the ideal solution to the worlds energy problems. The sun shines every day, they are relatively unobtrusive, they can be put in the places where energy is being consumed. The problem is, that for their cost, they can’t compete with other technologies. At the moment solar PV is primarily used on road signs and remote installations, places where the cost of running an electric cable is prohibitive, but for generating electricity for your home, the other technologies win out.

NOTE: Technology is moving forward fast… don’t give up on it just yet. Check out this site for an ongoingcommentary

GreenNav Supports the Niall Mellon Township Trust

March 24, 2008

Having hummed and hawed for a while about advertising here at GreenNav, I think we’ve come upon a plan that will work well. The site is now “supporting” the Niall Mellon Township Trust. We still won’t run ads (unless people tell us they think it is appropriate) , but are encouraging visitors to support the charity instead.

People can support the trust in one of 4 ways

  1. Volunteer to go to Capetown. Last year Patrick went on the trip and was very impressed
  2. Click the link on our site and donate money directly
  3. Donate money to some other volunteer. They aim to have over 2000 volunteers this year so I expect you’ll all probably know someone
  4. Come to the event we plan on holding in a bit, you can donate then!

Thanks to all for your support in advance


Irish Township Trust

Understanding Solar Panels 1 – Solar Thermal

March 21, 2008

Solar thermal energy systems absorb the sun’s light and transfer it to hot water which can be used for washing or cleaning. The main part of the system is the solar collector.

Understanding solar panels 1

Solar Collectors

Solar collectors are essentially black metal plates, which are heated by the sun’s energy. The metal then transfers the heat to liquid (usually come sort of anti-freeze) which is used to move the heat to a usable place, by being circulated to the domestic hot water cylinder. There is usually a sheet of glass placed above the metal plates to reduce loss of heat to the air.

Understanding Solar Panels

Hot Water Cylinder

The standard procedure for operating a solar thermal energy system, is to add another heat exchanger to the hot water cylinder (it probably already has one for the boiler) or change the cylinder for a system which already has multiple heat exchangers. The control system for solar panels monitors the temperature at the panel, and provided the temperature is sufficiently high, circulates the transfer fluid to bring the heat down to the cylinder.

So how well does it work?

The objective of Solar Thermal systems is to generate hot water. This does not mean heating, but hot water. In a domestic house the heating demand is mainly in the winter, when solar panels do not work that well. There is a hot water demand all year round however. So once you realise that that is what they are trying to achieve, they are great. Most people suggest they provide all the house’s hot water demands in summer, and over half in winter. Some are even more impressed with them, but it is fair to say that the reduction is in the region of 75%.

Furthermore Solar panels generally replace electrical energy, which as we saw before, is the most expensive and dirtiest type of energy.

More: Flat Bed or Evacuated Tubes

Energy loss from Windows

March 20, 2008

Considering their relatively small size, windows lose a frightening amount of energy. In fact, per square metre nothing in your house loses more energy. This is because when compared to other building materials, glass is a poor insulator. In one example I looked at recently, for the same area of wall and window, the window will allow up to eight times more heat to escape.

Everyone knows that the standard for new windows these days I double glazing, but why? Well, it is mainly because of the space between the two panes of glass, but it essentially stops the two main types of heat transfer.

Convection. Convection refers to the motion of a fluid (be it a gas or a liquid) from a hot place to a cold place. If you pour some hot water into some cold water, the two mix, through convection, until they are both at the same temperature. Similarly, the air in your house, which is hot, tries to mix with the air outside your house which is cold. By being air tight, the window stops this heat transfer.

Conduction. Conduction refers to a materials ability to transfer heat through it. A poker in a fire is a good conductor. Touch the poker and it is hot, even the part which is not in the fire. Plastic is a bad conductor. That is why a plastic handle on the poker will reduce how hot it is significantly. Air which is trapped in the space between the panes, is a really bad.

So… Double glazing reduces heat loss by reducing convection, by being air tight, and conduction, by using air in space between the panes. Generally speaking, double glazing reduces heat loss through windows by 50%.

Next… gas filled double glazing. In gas-filled double glazing the cavity between the two panes of glass is filled with an inert gas (usually argon) which conducts less heat than air, therefore improving the window’s energy efficiency. Argon filled glass reduces heat loss by about another 5%

Low emissivity or low-e type glass is where an invisible layer of insulation is place on the outside face of the internal glass pane of the double glazing. This special material, allows light to pass through it while very little heat is allowed to pass out. When light hits the opaque surface much of its energy is turned to heat. As heat has a much longer wavelength than light, the specially applied coating on the glass prevents the heat energy from escaping. Low-E double glazing can reduce heat loss by a further 18%.


Energy loss from windows

So if we add this all up, you’ll find that Low-E, argon filled, double glazing can reduce heat loss by about 73%. From a comfort point of view alone… a big winner.


Which HD TV is the most energy efficient?

March 18, 2008

Which HD TV is the most energy efficient?

Was talking to a friend recently about energy efficiency and TVs. So after a little digging I found this excellent article at Cnet. It shows the electricity consumption of a range of HD TVs, and despite making improvements, Plasma screens still trail LCD screens by almost a third. It also shows the standby power consumption of each. And that is amazing.

Different TVs standby power consumption 1/10th of 1% of the switched on power, to 23% of the switched on power. This range is incredible. In other words some TVs consume 230% more while on standby than others. And if you leave your TV is on standby for 20 hours a day, it is consuming more electricity waiting for you to use it, than when you are watching it.


Otherwise, CNET have some great suggestions on how to reduce your energy consumption by you TV, such


Turn the TV off when it’s not being used
Sure, this one’s obvious, but it’s easy to get into the habit of leaving the TV on as “background” when you’re not really watching it. And while TVs still consume power in standby mode, it’s a tiny fraction of what they draw when they’re actually on. Old habits die hard, but you’ll be saving yourself some bucks if you remember this tip.

Turn off the Quick Start option
Many HDTVs have an option called Quick Start or something similar, which makes the TV turn on more quickly when you press the power button. The flipside of this mode is that when engaged, it consumes significantly more power (typically 25 to 50 times as much) during standby, which can really add up. Do your energy bill a favor and turn this mode off. That few extra seconds wait for the TV to warm up is well worth it.

Turn down the LCD’s backlight
Many LCDs give you the ability to control the intensity of the backlight in the TV. By turning down the backlight, you’ll lower power consumption, but also make the TV less bright. While retail stores love to turn the backlights up all the way for their displays, we find that we get the best image quality when we turn down the backlight significantly.

Turn on the power-saver mode
Many TVs these days come with a power-saver mode that’s designed to cut down the power consumption. Performance of this mode varies from model to model, with the effect sometimes being drastic and other times providing only a slight savings. The only downside is that the power-saver mode usually makes the TV less bright, but we’ve found that sometimes this has a beneficial effect on the image quality, especially with the room lights turned off, in which case it’s a win-win situation.

Reduce light output with other settings
Many people buy a TV, turn it on, and never think to change the picture settings. Not only is that bad for the picture quality, it’s bad for power consumption. Most TVs are very bright by default, and that leads to using more juice. One of the first things a professional calibrator will usually do is turn down the light output–which is traditionally controlled primarily by “contrast” or “picture” controls–along with several other adjustments that will maximize the performance of your TV.

So what if you want some of the benefits of a calibration but don’t want to pay the dough? Don’t worry, CNET has you covered. All of our recent TV reviews are published with the settings our reviewers found appropriate for a completely darkened room–you can access them by clicking on “Tips & Tricks” at the top of a TV review (here’s an example of what they look like). Of course these settings aren’t optimized for your specific home theater equipment as a professional calibration would be, but they come closer than the default settings for most people.

How much savings can you get by reducing light output? The Imaging Science Foundation, an organization that provides professional calibration services, estimates that their calibrations can save 30 to 50 percent of your set’s current energy consumption. On the Panasonic TH-58PX600U that we tested before and after our own calibration, we found the power consumption drop from 442 watts pre-calibration to 318 watts afterward, a 28 percent drop.

Control room lighting
Many of these tips are going to make the TV less bright, but that can be compensated by controlling the light in your home theater room. While this may be a little overboard just for power consumption, limiting the light in your home theater also goes a long way toward creating the “theater” experience, as well as getting the most out of your TV.

And beyond TV concerns, good-quality blackout shades offer thermal benefits that keep other energy costs low; they keep heat in during the winter and keep it out during the summer.

Buy a smaller screen
If you’re looking to buy a new TV, you can limit your power consumption by buying a smaller set. This doesn’t always exactly hold–for example, rear-projection sets are often larger and draw less power than plasma TVs–but once you pick your display technology, going smaller will almost always use less juice. As always, you can compensate for smaller screen size, to a point, by sitting closer to the screen. Check out our rough screen size vs. seating distance guidelines for more info.

Watch TV together
Having multiple TVs in a house is more of a norm than a luxury these days, but that also means your power consumption is going to increase as well. You can cut that power consumption by watching with your family or housemates. You might need to make a few compromises on what you watch, but sometimes it’s more fun to watch with friends and family.

Watch less TV
Instead of sitting down for another dose of reality TV, you could opt for reality instead. Not only might you get some exercise, but you’ll be cutting your energy bill

Make a first step – video

March 14, 2008

How roof insulation works

March 14, 2008

Roof insulation is one of the easiest ways to reduce heat lost in your home and save energy. But how does it work?

how insulation works

Well firstly lets look at a piece of insulation. The most common types of insulation are blanket insulation and loose fill insulation. I’ll write another post on which is better, but for now, the two do essentially the same thing. They create a convection barrier to keep the hot air in.

Convection. There are 3 main ways in which heat is transferred. Convection refers to the motion of a fluid (be it a gas or a liquid) from a hot place to a cold place. If you pour some hot water into some cold water, the two mix, through convection, until they are both at the same temperature.

Similarly, the air in your house, which is hot, tries to mix with the air outside your house which is cold. Also if you figure that hot air rises, the roof is the most important place to stop it.

Conduction. Conduction refers to a materials ability to transfer heat through it. A poker in a fire is a good conductor. Touch the poker and it is hot, even the part which is not in the fire. Plastic is a bad conductor. That is why a plastic handle on the poker will reduce how hot it is significantly.

Air is a really bad conductor (remember though, air is a good convector)

So back to how insulation works.

Roof insulation is made of fluffy fibrous materials, that are good at trapping air in it (or at least slows down the air a lot). This air, is a rally bad conductor, and so reduces the amount of conduction going on. Since the air is essentially trapped, there is little opportunity for it to move, and so there is little convection going on. Boom. That is how insulation works

So why not just use a sheet of plastic? Plastic would work to stop convection, but it is would allow conduction to continue, and so be less effective.

So… in summary… insulation works by

  • Trapping air in (and so stop convection)
  • Using the trapped air to stop conduction

Tom Rafterys new energy blog

March 13, 2008

Just a quick one to pimp Tom Rafterys new energy blog. Tom has done a bunch of really cool work on his data centre, and consulted on energy matters with a bunch of others.

check it out