Solar Energy

Technologies and Project Delivery for Buildings

Andy Walker

• Publisher: RSMeans
• Year: 2013
• ISBN:
  9781118416549
• Edition: 1
• Topic: Architecture
• Subtopic: Conception architecturale

Solar Energy is an authoritative reference on the design of solar energy systems in building projects, with applications, operating principles, and simple tools for the construction, engineering, and design professional. The book simplifies the solar design and engineering process, providing sample documentation and special tools that provide all the information needed for the complete design of a solar energy system for buildings to enable mainstream MEP and design firms, and not just solar energy specialists, to meet the growing demand for solar energy systems in building projects.

1

Delivering Solar Energy Projects

Blazing overhead, the sun has always been an obvious source of energy. Early humans struggled against nature’s numbing cold and wilting heat, flood and drought, predation and starvation. Newton and Einstein’s understanding of force and energy has harnessed nature to elevate the life of the common man to a level of comfort that would have been envied by a prince of old. But the scale of this energy consumption has unintended consequences’the extent to which we are just now starting to find out about. All evidence is that primitive man bested nature in his struggle, and now, in a reversal, modern man must struggle to save nature’s fragile life.

Solar energy contributes to that preservation effort, and this book can help you make a difference by using solar energy to reduce a building’s demand on resources and its impact on the environment. Solar is clean and inexhaustible. It is distributed over the globe. Its availability is greater in sunny locations, but much of the world’s population and expected growth is in those sunny areas. And in cold locations, there may be less sun, but there is a greater need for heating, so it is possible to use more of what solar heat is available.

HISTORY AND CURRENT USE OF SOLAR ENERGY

Solar has been used as a source of useful energy from early man, to the industrial revolution, and on into the space age. Hero of Alexandria is credited with inventing the first solar-powered water pump in the first century AD. A French inventor named Augustin Mouchot demonstrated a focusing solar reflector at the Universal Exposition in Paris in 1878 that he used to pump water, distill alcohol, cook food, power a printing press, and affect an absorption cooler to make ice. Remarkably, this same nineteenth-century inventor later used solar heat focused on junctions of dissimilar metals to create electricity and split water, producing hydrogen, which he stored as fuel. The inventors of semiconductor diodes at the dawn of the electronics age investigated solar photovoltaic cells as one of the first applications (Butti and Perlin 1980). And now, we find solar powering space satellites and vehicles exploring Mars. We take a closer look at the history of each technology at the beginning of each chapter.

Nowadays, the world runs on fossil fuels: coal, petroleum liquids, and natural gas. Figure 1-1 displays data from the International Energy Outlook 2011, an analysis published by the US Energy Information Administration, showing energy consumption of oil, natural gas, coal, nuclear, and other fuels from 2005 to 2012. Natural gas is seen to gain market share because it is a cleaner burning fuel and two extraction technologies (directional drilling and hydraulic fracturing) have increased supplies. Solar energy is counted among the “other” fuels and is increasing as well.

Of the 542 quads of energy consumed in 2012, solar accounted for only 0.1 quad. Figure 1-2 shows how that consists of solar thermal and photovoltaic applications in utility electricity, commercial uses, and residential buildings.

Figure 1-1. This chart of global annual energy consumption by fuel type (109 GJ, quadrillion Btu/year) shows the recent increases in the use of natural gas and renewable energy. (Figure by the author using data from US Energy Information Administration 2012)

Figure 1-2. Global annual consumption of energy from solar energy applications has been increasing rapidly, with residential and utility-scale photovoltaics showing the most rapid growth. (Figure by the author using data from US Energy Information Administration 2012)

One may surmise that solar energy’s contribution to world energy use is small, but what is exciting is that it is increasing rapidly. In 2012, solar electric generation increased 24 percent, a rate that has been sustained for several years now. On a percentage basis, solar is the fastest growing electric-generation resource. Figure 1-3 shows recent growth in solar electric generation capacity (GW of installed capacity) by country. For the years from 2010 to 2035, the US Energy Information Administration (EIA) predicts an average annual growth rate of 16 percent for utility photovoltaics and 11 percent for residential photovoltaics. According to this projection we should be busy designing and installing solar energy systems for some time to come.

Figure 1-3. The cumulative generating capacity (GW) of solar electricity has demonstrated exponential growth, led by Japan and countries in Europe. (Figure by the author using data from US Energy Information Administration 2012)

ADVANTAGES OF SOLAR ENERGY

The main disadvantages of solar energy systems on a building are the high initial cost to purchase and install, ongoing operation and maintenance, and the risk of a failure in equipment performance. Solar also has many advantages that occur in a variety of ways to help us preserve the environment and meet our financial goals. In discussions among various stakeholders, the following advantages of solar energy are often cited:

Provide a Financial Return on Investment

Solar energy can be the least-cost option in a place where conventional energy is very expensive, such as in a location that relies on oil as a source of energy. Sunlight is delivered to even remote locations for free, so a solar project saves the cost of fuel, delivery costs, and cost of operating the conventional energy system. It is expensive to operate an electric generator in a remote location, and until 2004 such remote power applications were the largest part of the solar energy market. Since 2005, tax credits and other incentives have lowered the cost of solar energy projects to the point where utility cost savings (in not-remote locations) are sufficient to pay back the initial cost in the system with a favorable rate of return and manageable risk to the investor. Sophisticated investors serve the solar market’they combine utility cost savings, tax credits, and other incentives to construct cost-effective projects. Large projects involving third-party financing are responsible in large part for the growth in the solar market from 2005 to present.

Safety and Security of the Energy System

Solar is often added as a second source of energy along with conventional fossil-fuel systems. Depending on how the system is configured, this may serve as a redundant energy source. For example, the pump on my natural-gas-fired boiler recently failed, but I didn’t have rush to get it fixed because the solar heating system provided the heat we needed. Solar electric systems may also be configured with batteries to provide power to dedicated circuits in a utility-power outage.

Recent news has been filled with tragedies related to energy. An offshore drilling rig exploded in the Gulf of Mexico, killing 11 workers and ruining the habitat with over 170 million gallons of toxic crude oil in 2010 (NRDC n.d.). Based on tracking plumes of isotopes such as iodine-131, accidents at nuclear plants in Fukushima, Japan in 2011 and Chernobyl Russia in 1986 will each be blamed for 500, 000 deaths all over the world, mostly among infants less than one year old (Mangano and Sherman 2012). Little doubt remains that emission of carbon dioxide into the atmosphere from fossil-fuel use is causing a warming of the planet, with consequential changes in the climate. These catastrophic failures expose systemic distortions that high profits insert into the equation of risk versus reward (the profit being private, the risk being public).

I can’t think of any way that solar could ever cause a disaster of such proportion. It is distributed and not concentrated into one facility. And while there are general safety issues related to electric systems and some hazardous materials in batteries and some types of solar collectors, solar involves no risk of explosion or of large release of toxic contaminants. While most solar systems are not designed to operate independently, they certainly can be, and if they are they contribute essential power in an emergency. Solar power systems don’t require delivery of fuel in an emergency, such as a diesel-fueled generator would. Solar energy systems are located at the use of the energy, thus avoiding risk associated with failure of a large transmission and distribution system. The issue of safety and security spans all the way from an electrical outlet in a home in America to the Middle East. A complete calculation of the cost and risk of fossil fuels would have to include national security and international actions to secure stability in energy markets.

As a technological society, the tools that we have include education, incentives, and regulations; and we can use these tools to correct extreme risks before catastrophic failures occur and to limit the damage when things do go wrong.

Less Pollution than Fossil Fuel

The myth persists that environmental damage may be “externalized” from cost in such a way that the profits are private but the damage is to the commons. The related deception is that the environment is limitless in its capacity to absorb pollution. The truth is that the environment is already at its capacity, and any further mistreatment has traceable consequences to human health. We are a technological society, so we can invent solutions to how processes interact with their surroundings. And we are civilized, so we can work together for the common good.

WARNING

Safety First

Solar energy systems involve hazards encountered in any heating or electrical system, plus some encountered uniquely in solar systems. Safety should be considered during site visits, and in considering features of the design, special measures during construction, safety in long-term operation maintenance procedures, and safety in disposal of materials. General safety requirements on the worksite include helmet, safety glasses, vest, and work boots. Solar work requires long-sleeved shirt, long pants, sunscreen, and that the helmet be opaque and reflective. Roof safety is of particular importance. Roof safety usually limits access to the roof during site visits and requires different “fall protection” systems (railings, ropes) during rooftop activities and construction. Roof access for firefighters must be considered in consultation with your fire marshal when locating the solar collectors on a roof. Electrical safety applies to all parts of a photovoltaic system and entails two special characteristics of PV: 1) they are energized and cannot be turned off whenever the sun is shining and; 2) the short circuit current is not much greater than the expected operating current, so an arc can be sustained as electrical connections pull apart without tripping the breaker protecting that circuit against high current. “Arc-flash” protection is required when working on energized circuits and involves special gloves, as well as face and body coverings. “Lock-out tag-out” is a procedure to make sure nobody energizes a circuit someone else is working on. Sanitation is key to solar water heating systems, as they are often used to preheat potable hot water, and large volumes of water at tepid temperatures provide a media for bacteria, a risk that can be reduced by use of a load-side heat exchanger that does not store potable water. Some components used in solar energy systems involve toxic materials. The acid used in flooded batteries may be the most dangerous, but lead in batteries, cadmium in some types of photovoltaics modules, and spent heat-transfer fluid require custody over the life cycle of the material to properly recycle.

After hiking up to a rise above Everest base camp in Nepal, at 5.5 km above sea level (18, 200 ft), I could look down on as much of the mass of the atmosphere as up. Almost half of the atmosphere’s mass is below that elevation. The thinness of the atm...