Month: June 2014

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apartment living building design energy

Passive Design for Lighting

One immediate way that we can cut our CO2 emissions is to just use less energy. Since our homes and other buildings are huge energy users they are good places to start. By using passive design practices, we can build and maintain more energy efficient homes by using energy from the sun or the ground instead of energy from the grid to serve our needs.

Natural Light and Proper Siting

Using the sun to provide most of our light can reduce the amount of electricity we use and can save money – both on our electric bill and in the cost of light bulbs.

The best time to think about using natural light in place of electric light is before construction. At this point, thinking about window placement can provide a building with adequate light for much of the day. In the summertime, well placed windows and an open floor plan can provide for plenty of light well into the evening hours.

To this end, siting a house properly can be very effective in providing natural light. We often think that the face of a house must be parallel to the street, but depending on the direction that the street runs, this may not be the best position for the windows and the walls. Taking into account the cardinal directions and the angle of the sun throughout the year can help determine the optimal position of windows to take advantage of natural light.

Continuing in this vein, thinking about the layout of the rooms in relation to how and when they will be used during the day before building can help optimize the use of natural light in a structure after it is built.

South facing windows

South facing windows are the workhorse of passive lighting in the northern hemisphere (in the southern hemisphere it would be north facing windows). Because of the tilt of the earth’s axis, in the northern hemisphere the sun is angled to the south. A south facing window, then, receives light throughout the whole day, not just in the morning or evening. South facing windows are put to best use in rooms that will be used all day long.

East facing windows

East facing windows receive the strongest light in the morning, and thus are best positioned in rooms that are primarily used in the morning through late afternoon, such as an office. If you are an early riser, you may prefer to have east facing windows in your bedroom. However you may not want east facing windows in a nursery if your baby wakes with the sun, or in your bedroom if you prefer to snooze a bit later in the morning or work the night shift.

West facing windows

West facing window are pretty much the opposite of east facing windows when it comes to lighting. (I’ll get into the differences in the heating and cooling sections of this series.) They are best positioned in rooms that are used in the evening, as they will provide the most light during the later part of the day. I do a lot of cooking in the evening, so I prefer to have a kitchen with western facing windows.

North facing windows

Due to the earth’s tilt, northern facing windows will receive the least amount of sunlight, and thus are useful in rooms that are used primarly during the middle of the day, or in rooms that are meant to be kept darker. An office might be the right choice for a room with north facing windows. Or maybe this means that depending on your sleep habits and preferences, north facing windows would work well in your bedroom. If you are building a basement cellar and your basement has windows on all four sides, choosing the north wall to build your cellar against makes the most sense.

Skylights

Skylights can go a long way to lighting a room in the middle of a house. Depending on the direction they are positioned, the pitch of the roof they are installed in, and how far north or south the building is, they will provide different amounts of light during the day or evening.

So directionality and placement of windows is something that can be considered before a structure is built, but afterwards can be quite costly to change. Here are a couple examples of what can be done to improve passive lighting in your already built home or business:

Curtains

Using sheer and light colored curtains during the day can allow light into a room while still providing a bit of privacy. They can also help temper the strong rays of a rising or setting sun on east and west facing windows.

Mirrors

Well placed mirrors can help spread light into darker areas of a room or into a windowless hallway.

Wall paint

Light colored paint will reflect more light around the room, whereas darker colors will absorb more light. So if you are partial to bold wall color but don’t want to greatly reduce your ability to use passive lighting, put the color in a room with south facing windows or with windows on multiple sides. Dark and light colored flooring can be used to the same effect.

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Are you looking for an introduction to passive design? You can find it here.

Oh, hey, Building Earth has a facebook page now.  Keep up to date on posts and other interesting green news by liking us!

Categories
building design energy

An introduction to energy efficiency through passive design

The building industry uses about 75% of electricity production in the US. This means that if we can make our building-related-energy-use more efficient we can make a big dent in the amount of electricity that we need to produce, and thus make a dent in the amount of greenhouse gas emissions we are releasing into the atmosphere by burning coal and natural gas to make electricity.

Energy efficiency in our homes can come a few different forms, but for the next few weeks I will be focusing specifically on energy efficiency through passive design. To start, let’s break it down. Energy efficiency means using less energy to achieve the same ends. In terms of buildings, I am going to focus on are lighting, heating, cooling, and water use efficiency. Passive design is when a building is built in a certain way so that you don’t have to use energy to save energy. For example, using sunlight to light a room is a passive design element because the sun is already there. You don’t have to add any energy into the system (the building) to produce light. Using an LED light bulb to provide light is an active design element because, while you are using much less energy than a filament bulb or CFL, you are still adding energy to light the room with the LED.

As you might guess, the best time to incorporate passive design elements into a building is before it’s even built. But there are some things you can do to an already existing structure to make it more energy efficient through passive design. I’ll be sure to cover both areas as this series continues.

As always, if you have any questions up front about passive design, send them my way and I’ll do my best to answer them as we go.

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Oh, hey, Building Earth has a facebook page now.  Keep up to date on posts and other interesting green news by liking us!

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energy

Energy Round Up

I hope that over the past couple months I’ve helped you’ve gained a greater understanding of all the ways that we make electricity. To sum things up, I’ve put together a little chart to help compare and contrast the various energy sources we use.

current % in USA potential supply based on current use $/kWh cost of power plant average lifespan notes
conventional fossil fuel 67% known coal reserves will last ~200 years 0.02-0.05 $1 billion per plant 30-40 years produces ~40% of total CO2 emissions
clean coal / carbon sequestration 0% known coal reserves will last ~200 years 0.08-0.12 $5 billion per plant 30-40 years long term storage of CO2 has many unknowns
nuclear 20% 230 years with current technology at current production rate 0.03 $5-6 billion per plant 50-70 years containing and cooling radioactive material is an ongoing challenge
hydro 7% 16% 0.03-0.05 $2-3 billion per plant 50-100 years low cost and low mantenance, but disrupts ecosystems and communities that rely on the river
geothermal less than 1% 7% 0.01-0.03 $2-4 million per MW 30-40 years location matters; deep drilling is difficult and expensive; earthquakes
wind 4% 20% 0.04 $1-2 million per MW 25 years wind can be unreliable; best location is rural, but requires good transportation of electricity
solar 0.2% all of it forever and ever, or at least until the sun explodes 0.12-0.17 $4-6 million per MW 20-40 years efficiency, cost, and waste need to be improved

Just about 2 weeks ago the EPA released it’s preliminary regulations for CO2 emissions for electricity production. These regulations will be a good step in the right direction for America, one of the top most countries producing CO2. Making the changes necessary to cut our emissions will come with growing pains for sure. There is no one right answer to slowing or halting global climate change. Instead we need to use all of our tools, and that means it is important for us to know what tools we have.

The fastest way we can cut the CO2 emissions that come from electricity production is to use less electricity, and use it more efficiently. In that vein, in the coming months I’ll be exploring energy efficiency, and in particular passive design. Stay tuned!

…
For an introduction on sources of electricity, look here.
For an explanation of how we make electricity, look here.
Clean Coal
Nuclear Energy
Hydroelectricity
Wind Power
Geothermal Electricity
Solar Power part 1
Solar Power part 2

Oh, hey, Building Earth has a facebook page now.  Keep up to date on posts and other interesting green news by liking us!

Categories
energy

Solar Power part 2

learn all about solar powerWhat Solar Power is:

Solar power is electricity made from the sun’s energy that reaches the earth. Fun aside: wind power, fossil fuels and biofuels are all ultimately made from the sun’s energy. But only solar cells directly change the sun’s light into electricity.

How Solar Power is made:

See Solar Power part 1, The basics: light from the sun hits a semiconductor and provides enough energy to make free electrons jump.

How much of our current electricity is produced by solar power:

In 2013, the US used over 8,000 MW hours of solar electricity. That is about 0.2% of the total electricity in the US.

Potential energy supply:

In one year, the entire world uses about 15 terawatts (a 15 followed by 12 zeroes) of electricity. That’s the same amount of sunlight that hits the earth in one hour. In other words, enough sun light hits the earth in one hour to provide electricity for everyone for one year! However, the challenges are collecting this energy, turning it into electricity, and storing it for use when needed (and not just when it’s sunny outside). But there is hope, Germany just reported producing 74% of their energy from renewables, and solar power played a large roll.

Materials and how we get them:

Solar cells are made of silicon crystals and silicon is the most abundant element on earth. However, it is almost always bound to oxygen in a molecule commonly called “sand” or “quartz”. We use electricity to get rid of the oxygen. The silicon is then heated and stretched like taffy. This stretching  draws impurities to one end. The impure end is removed and the remainder is pure enough to make solar cells. The pure silicon is then made into single crystal wafers and other elements are added.

Silicon is very shiny and reflective, which is not useful for collecting light. Titanium dioxide is used to help the silicon absorb more light.  Titanium dioxide is mined throughout the world.

The cells are sealed into rubber, put into an aluminum frame, and covered with a glass or plexiglass protective sheet.

Waste produced and how we deal with it:

Creating silicon wafers for solar cells is quite energy intensive because of the need for purity. A lot of heat and electricity is used in the process, which does produce carbon dioxide. Additionally, the manufacturing process makes industrial sludge and toxic waste, which need to be trucked to waste management sites for cleaning and containment.

Solar power produces no carbon dioxide after the cells have been made. However, the industrial wastes and CO2 produced during manufacture of the solar cells are siginificant. It is important for us to pursue cleaner and better managed outputs, as well as producing cheaper,  more efficient solar cells.

Cost:

Large scale solar power plants currently produce electricity at the cost of about $0.12-$0.17 per kwh to the customer. The cost of installing solar panels onto the roof of your house is typically about $7-$9 per watt. A 5kW (the typical household consumption) array costs about $30,000. The good news is that it is estimated that solar will cost the same as fossil fuels within the decade. However, we need to act now to start combating our use of fossil fuels.

Challenges:

As I’ve mentioned above, cost and waste are both currently challenges to solar electricity. These challenges will be addressed by making solar cells that can more efficiently turn light into electricity. Currently, solar cells are able to convert about 20% of sunlight into electricity. Nearly 45% efficiency has recently been achieved by researchers in Europe. Being able to mass produce solar cells with that much efficiency will drive down the cost and reduce the number of solar panels needed to produce the amount of electricity that we use, reducing waste as well.

…
For an introduction on sources of electricity, look here.
For an explanation of how we make electricity, look here.
Clean Coal
Nuclear Energy
Hydroelectricity
Wind Power
Geothermal Electricity
Solar Power part 1

Oh, hey, Building Earth has a facebook page now.  Keep up to date on posts and other interesting green news by liking us!