Ériton Luis Santolin | Universidade Federal de Viçosa (original) (raw)

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Figure 1. Photograph of house with a view of the new south wall and showing the solar panels on t... more Figure 1. Photograph of house with a view of the new south wall and showing the solar panels on the roof. Energy is an important topic in today's world. Dependence on petroleum and coal has had many side effects, including air pollution, global warming, and political strife between oil-producing and oil-consuming countries. Many people are concerned about the increasing costs of energy. To illustrate some possible actions individuals can take, we will describe the process we went through on our house to reduce our energy consumption and to use renewable energy sources. Our house is a two-story ranch style built in 1985 (see Figure 1). It was fairly energy efficient for homes in that era, having R-19 insulation in the walls, double-paned windows, and a high-efficiency gas furnace. 1 One thing the house did not have was a wood stove. We enjoy having a wood fire on cold days, and there are many of those days here in Wisconsin. Also, wood is a renewable fuel source and is nearly CO 2 neutral, so it does not increase global warming. So we began to plan a remodeling project to include a wood stove. The project grew when Betsy suggested we add a plant room on the south side of the house. With the southern exposure we thought we could have enough passive solar energy collection to keep the plant room warm year round. As we talked more about our energy consumption, we decided to do as much as possible to reduce our use of fossil-fuel based energy. This would involve energy conservation and use of renewable energy. Our first step was to have a renewable energy site assessment, which we did in June 2003. We are fortunate that the state of Wisconsin has a program to encourage the use of renewable energy. Trained energy auditors visit your home and conduct a site assessment at a very reasonable cost. The Wisconsin Focus on Energy Web site 2 has information on various Wisconsin energy programs. Many other states have similar programs. 3 The items we were interested in were: • Passive solar energy collection in the new plant room • Solar hot water heating • Solar photovoltaic energy collection and conversion • Wind energy generation • Heating and cooling with a geothermal heat pump • Using a wood stove for heating Passive Solar Design Passive solar collection is one of the most cost-effective ways to reduce your energy consumption. By considering the sun's position you can design elements into your house that maximize solar heat gain during the cold season and minimize heat gain during the warm season. We hired an architect experienced in passive solar design to assist us with our project. Three main considerations are the windows, the overhang of the eaves, and the thermal mass. We added a sun room/plant room on the south side of our house because we needed a lot of sunlight for the plants. The room is earth-bermed two feet high on the outside to reduce heat loss through the walls. Exhaust fans were added in the ceiling to provide ventilation during the summer. Window size, position, and type all affect solar thermal gain. We chose double-paned, argon-filled, low-e (emissiv-ity) glass. For the plant room we used all vinyl windows because of the high humidity in that space. In the rest of the house we used wood windows with exterior vinyl cladding. The roof overhang is a key element of our design. It extends far enough to block direct sunlight during the summer, yet allows as much direct light as possible in during the winter. This is possible, of course, due to the tilt of Earth's axis and the sun's varied position in the sky during the year. The amount of overhang necessarily varies with latitude. A passive solar design generally incorporates a way to store heat during the short days of winter and to release this heat to warm the room during the long night. Objects with high thermal mass can provide this storage. They are materials with high mass and high heat capacity. For our room we poured a 0.30 m thick slab of concrete for the floor. We insulated under this slab to minimize heat loss to the ground. The back wall of the plant room is limestone, which also provides a large thermal mass. Water storage barrels can also help to moderate the temperature swings. Solar Hot Water Heating Solar domestic hot water (DHW) heating is a great way to incorporate renewable energy into your home. Modern systems are very reliable and the cost payback is very reasonable. A DHW system consists of solar collector panels in a sunny location, typically on a roof, a storage tank with a heat exchanger, a pump to circulate the fluid, and some simple controls (see Figure 2). We have four panels on a south-facing roof. The panels have a total surface area of 8.2 m 2. Support

Meeting global energy needs in a sustainable and environmentally responsible way is one of the gr... more Meeting global energy needs in a sustainable and environmentally responsible way is one of the grand challenges of our time. While the use of energy based on fossil fuels has enabled great advances and an increase in the standard of living, it has also brought us to the brink of an environmental catastrophe. As a society, we will need to develop strategies that integrate renewable and sustainable energy sources. We must also engage and partner with policy makers in order to articulate an energy policy that is not only scientifically and technically sound, but also one that the global society will accept. The energy challenge is the type of problem that we, as a global society, have never faced before and we need decisive scientific and political leadership to address it. We must accept the challenge and insist that our leaders articulate a global energy policy capable of meeting such a challenge. (Image created by Alice Muhlback and used with permission.) E nergy: its mere sound evokes a broad range of reactions depending on our experience, education, political affiliation , and many other factors. The word is part of our everyday lexicon in terms of the cost of energy (when we actually mean the cost of fuel), global availability of energy and the inevitable geo-political analysis, the environmental consequences of energy use, carbon footprint, global warming, emerging economies, population growth...you get the idea. Energy is part of virtually every aspect of our lives, local and global. Energy is also a subject of big numbers such as "quads" (quadrillion BTUs), Terawatt-years, and gigatons (usually of generated CO 2). As chemists, actually as citizens (better yet, as informed citizens), we need to grapple with these concepts and the magnitude of these numbers to get a realistic assessment of what they mean and how our collective behavior affects them and the future of our planet. (See Figure 1.) Energy availability, in a reliable and inexpensive way, has been key to technological advances and innovation, which, in turn, have enhanced our standard of living. One can readily identify and acknowledge that developments such as the steam engine, the incandescent lamp, the internal combustion engine and the computer, just to name a few, have transformed the way we live and interact with each other. All of them have a common thread of depending on an energy source, albeit different in each case, to accomplish a particular function. This brings us to the description of energy in terms closer to those associated with thermodynamics, mainly as the ability to do work. So the question is, how are all of these issues interrelated, and what role do we, collectively, play?