Green Engineering

Date 11/17/11 | | Name: Manuel Tejada Activity: Sustainable Architectural Design Course: Materials and Processes (CD220) Instructor: Paul Debashis Green engineering is a much-needed approach to transform existing engineering disciplines and practices to those that promote sustainability. The concept of sustainability is to develop and implement technologically and economically viable products, processes, and systems that meet the needs of humanity, while protecting the environment.

Green engineering is governed by the following principles: Use the least amount of energy to achieve any given task. Generate as much energy as possible using renewable resources. Generate the least amount of pollutants and by-products during energy generation. Use renewable and biodegradable materials to a maximum extent for building structures and fabricating products. Reduce waste during construction and fabrication. Design structures and products to maximize their life ps and minimize maintenance.

Design for easy deconstruction and facilitate the reuse of components and materials from obsolete structures and products in new construction and fabrication. Make the least impact on the environment. The obvious question is: Why are these principles not followed? The answer is: Because of economics, convenience, ignorance, and affluence, with economics playing the major role. For example, thermal power plants are still a more economical source for electrical energy compared to solar energy.

However, the depletion of raw materials and the cost of controlling pollution and by-products are resulting in a steady increase in the cost of electricity produced by thermal power plants. This, in combination with the improved efficiency of solar cells, is making solar cells a viable alternative. In the area of energy production, the fraction of energy produced by renewable resources is still very small. The popular sources are coal, natural gas, oil, and nuclear. Hydroelectric power plants are a long-standing renewable source.

The growing sources of energy production are solar and wind. Fossil fuels generate carbon dioxide and large amounts of residues, such as fly ash and bottom ash. Philosophically, most of the energy we are using came from the Sun. For example, coal, oil, oil shale, and tar sand were produced over millions of years from forest growth. If we could harness solar radiation, then most of the world’s energy needs could be met. To achieve this, the efficiency of solar cells has to be increased considerably.

It is estimated that the Sun provides about 120 quadrillion watts of energy daily, while worldwide consumption is about 13. 5 trillion watts per year. In the next paragraph I will present the proposed of solar panels for a small business in Dominican Republic (Karina supermarket), which spends about 2160 kwh every month (0, 35 usd/kwh) $ 756 us monthly. For this project we are going to use solar panel that contains 4 cells, and each of them can produce 0. 45 volts and 100 milliamps, or 45 milliwatts. Each cell measures 2 inches by 0. 5 inches.

In other words, with these solar cells you can generate 45 milliwatts in one square inch (6. 45 square cm). For the sake of discussion, let’s assume that a panel can generate 70 milliwatts per square inch. To calculate how many square inches of solar panel you need for a Supermarket, I need to know: * How much power the supermarket consumes on average. * Where the supermarket is located (so you can calculate mean solar days, average rainfall, etc. ). This question is possible to answer because I have the specific location in mind.

Considering that in the tropics the days are longer and the sun shines more. We’ll assume that on an average day the solar panels generate their maximum power for 6 hours. Now we are going to do some calculation of how much solar electricity I need to power this supermarket. This means that what I would be powering with solar electricity are things like the refrigerator, the lights, the computer, the TV, stereo equipment, motors in things like furnace fans and the washer, etc. Let’s say that all of those things average out to 3000 watts on average.

Over the course of 24 hours, you need 3000 watts * 24 hours = 72,000 watt-hours per day. From our calculations and assumptions above, we know that a solar panel can generate 70 milliwatts per square inch * 5 hours = 350 milliwatt hours per day. Therefore you need about 205,000 square inches of solar panel for the supermarket. That’s about 5 solar panel that measures about 285 square feet each one (about 26 square meters). The cost for each unit, including battery bank and installation $16,000-$20,000 us. Now we are going to compare the annual cost of both system solar panel Vs regular energy.

Solar Panel Total energy peer year: (2160kwh/m) (12m) = 25,920kwh/y Total installation cost: (5panel) (20,000us) = $100,000us Total cost kwh: Total cost/Total energy peer year = $3. 858 us/kwh Regular energy Total energy peer year: (2160kwh/m) (12m) = 25,920kwh/y Total Cost: (25,920 kwh/y) (0, 35 usd/kwh) = $9,072 us Assume no change in the cost of the electricity and base in the calculation, this system will likely pay off in about 11 years. The average lifetime of solar panels is 40 years, so your investment will reap about 3 times the initial cost.