Bonding+in+more+detail

=Bonding in more detail - Solids=

Overview __**Liquids**__

Caption: The formation of a spherical [|droplet] of liquid water minimizes the [|surface area], which is the natural result of [|surface tension] in liquids. Retrieved from: wikipedia.org

A cannonball floats in mercury. []

__**Molecular Solids**__

Hydrocarbons are usually molecular solids.

(Retrieved from Wikipedia) //The term "molecular solid" may refer not to a certain chemical composition, but to a specific form of a material. For example, solid [|phosphorus] can crystallize in different [|allotropes] called "white", "red" and "black" phosphorus. White phosphorus forms molecular crystals composed of tetrahedral P4 molecules. [|[3]] Heating at ambient pressure to 250 °C or exposing to [|sunlight] converts white phosphorus to red phosphorus where the P4 tetrahedra are no longer isolated, but are connected by covalent bonds into polymer-like chains. [|[4]] Heating white phosphorus under high (GPa) pressures converts it to black phosphorus which has a layered, graphite-like structure. [|[5]][|[6]] // //The structural transitions in phosphorus are reversible: upon releasing high pressure, black phosphorus gradually converts into the red allotrope, and by vaporizing red phosphorus at 490 °C in inert atmosphere and condensing the vapor, covalent red phosphorus can be transformed back into the white molecular solid. [|[7]] // //of white phosphorus// || //Structures of red// || //and black phosphorus// ||
 * [[image:http://upload.wikimedia.org/wikipedia/commons/thumb/8/88/PhosphComby.jpg/280px-PhosphComby.jpg width="280" height="101" caption="PhosphComby.jpg" link="http://en.wikipedia.org/wiki/File:PhosphComby.jpg"]] || [[image:http://upload.wikimedia.org/wikipedia/commons/thumb/0/06/Tetraphosphorus-liquid-2D-dimensions.png/120px-Tetraphosphorus-liquid-2D-dimensions.png width="120" height="86" caption="Tetraphosphorus-liquid-2D-dimensions.png" link="http://en.wikipedia.org/wiki/File:Tetraphosphorus-liquid-2D-dimensions.png"]] || [[image:http://upload.wikimedia.org/wikipedia/commons/thumb/7/7b/%C4%8Cerven%C3%BD_fosfor2.gif/120px-%C4%8Cerven%C3%BD_fosfor2.gif width="120" height="34" caption="Červený fosfor2.gif" link="http://en.wikipedia.org/wiki/File:%C4%8Cerven%C3%BD_fosfor2.gif"]] || [[image:http://upload.wikimedia.org/wikipedia/commons/thumb/5/51/BlackPhosphorus.jpg/120px-BlackPhosphorus.jpg width="120" height="114" caption="BlackPhosphorus.jpg" link="http://en.wikipedia.org/wiki/File:BlackPhosphorus.jpg"]] ||
 * //White, red, violet and black phosphorus samples// || //Structure unit//

Carbon is a molecular solid Retrived from: [|http://molsim.chem.uva.nl]

Dry Ice (CO2) is a molecular solid:

__**Covalent Solids**__

__**Hydrogen Bonded Solids**__

__**Metals**__

Ionic solids are characterized as the easier bonds to model because they closely resemble idealized charges by Coulomb's law.
 * __Ionic Solids__**

__**Application - Molten Salts in Solar Reactors**__

Molten Salts ||
 * Physics background |||| Molten Salts
 * Alternatives to fossil fuel power generation are varied and interesting. Some technologies are straightforward, but others are mystifying. Molten salts are frequently mentioned in articles that relate to power generation, but they are seldom explored in detail. This paper discusses what a molten salt is, why it is ideal for power storage, and some of the chemical and physical properties that make it so interesting. || Physical features of cutting edge technology ||

Molten Salts in Solar Reactors =Overview= While there is growing awareness in “green” or “alternative energy”, traditional methods of capturing the sun’s energy have been around for some time. Solar ovens can be used to cook food, distill water, dry food for storage, and now recently, provide electricity for homes. Storing solar energy so that people have a consistent and reliable source of energy presents a central challenge to the emerging field. Photovoltaic, or “PV” technology only provides power in sunlight, but power needs are for 24hrs a day. A method of storing and providing power for a 24hr cycle is underway commercially in at least three locations worldwide. This method uses energy from the sun to heat up a large quantity of a substance, such as oil or a “molten salt”. Once enough heat is stored, it is used to produce electric power in the same way as fossil fuel power plants via turbines. Molten salts are frequently mentioned in articles that relate to power generation, but they are seldom explored in detail. This paper discusses what a molten salt is, why it is ideal for power storage, and some of the chemical and physical properties that make it so interesting. This paper also discusses some challenges that are in the field, and gives an overview of power production in the United States =Electricity Production 101= Homes, businesses, and industry all require reliable power to keep homes comfortable, businesses running, and industry moving forward. Numerous studies have shown the connection between the success of a nation and inexpensive, reliable power supplies.

The main method of power generation
Almost all power generation in the world comes from an early principal of physics: a spinning magnet creates electrical current. Known as Faraday’s law, it is how almost all forms of power are created. The spinning magnet apparatus is called a generator. The magnetic flux is the integral over the area.

Generally, water is boiled to create steam, and this steam spins a turbine, which then spins a magnet (Figure 1). The question then is, “how do we boil the water”. In a fossil fuel plant, coal, oil or natural gas is used to boil water and create steam. In a nuclear reactor, steam is produced by a controlled nuclear reaction. In a wind turbine, the steam process is bypassed, and the wind spins a magnet, which then generates power.

What is 1 Watt?
Power generation is measured in watts, and most power plants create hundreds of megawatts. Roughly speaking, if a person was to take a small apple or a smart phone and lift it one yard in 1 second, that power represents about 1 watt of power. Bear in mind that the power produced must be continuous. In order to produce 1 watt of power for 1 minute, that means the smart phone would have to be lifted a yard each second for 60 seconds in a row. This is why power is usually produced in a rotational manner. An incandescent bulb 100 watt bulb is about 22 lbs lifted 1 yard each second, a typical family home draws about 1,000 watts on average, and a large store, such as a Wal-Mart, draws about 1 million watts. The United States uses roughly 925 giga-watts on average in the summer and 750 gigawatts in the winter.

Sources of Power for the United States
The source of power to boil water mainly comes from fossil fuels, which are broken down into percentages below. Fully 8% is considered renewable, but The charts below, supplied by the Energy Information Administration (EIA) breaks down the supply sources and demand sources.

=Solar Overview= Over 86,000 terawatts of solar energy reach the Earth’s surface each year- enough to satisfy current global energy demand 1000 times over. In 2008, solar electric power amounted to a mere 0.2% of global energy produced but it is at a tipping point with a growth rate of 40% per year. Exponential growth, enormous solar resources and the global economy's unquenchable demand for electricity increasingly position photovoltaic power as vital to 21st century technology. Solar energy is captured in two distinct ways, photovoltaic solar capture and solar concentration which uses molten salts. The Photovoltaic power takes direct sunlight and provides power via the photoelectric effect. Photovoltaic energy, featured in the photo to the left at Arizona State University, capture has a serious limitation- energy is not captured during the night, and has minimal impact during peak power hours. Peak power demands generally are during sunrise and sunset, because power demands are at both residential and commercial applications. A pure photovoltaic plant requires some sort of energy transfer into potential energy for the non-daylight hours and low performing hours. Energy can be stored theoretically on a commercial basis by a variety of means. Commercially, energy is stored in the following ways; compressed air, such as pumping into a salt mine, raising water, or pumping into a reservoir.

Solar Heat Overview
Solar focusing plants change the sun’s into a heat. Below is figure 2.2, from the EIA which catalogues the number of heating modules that have been sold in the US. Because of the economic downturn and the sharp reduction of oil prices, sales have dropped but demand remains. The figure next to 2.2 from Sandia Labs features a power tower solar collection type.

Currently, there are at least three types of solar plants in operation, solar focusing, trough systems, and point focused. The diagrams of the three types are courtesy of the EIA.

Solar focusing to a central location and a mirror array
Also known as “power towers”, large tracking mirrors focus the sun’s energy into a central location. The mirrors, or “heliostats”, move with the sun and it has a concentration factor of over 800. Temperatures in the central tower can exceed 5,000 F. The advantage to this type of system is that power towers are the oldest and most well known type of solar collecting systems. Disadvantages are that since the mirrors are a long way from tower, and there is power loss due to the fact that the solar rays diffuse because they are travelling through large amounts of air, and power loss vialaw. It is also difficult to increase the scale of the operation easily. Solar focusing via circular mirror Also known as “Linear Concentrators, the sun’s energy is concentrated on a fluid filled tube (usually a synthetic oil), and the tube is along the focal line of the trough. It tracks the sun and has a concentration factor of 30-40. Circular mirrors focus the sun’s energy on to a pipe. They are low to the ground. Circular mirrors easy installation and easy maintenance. It is possible to easily increase scale of a power plant by addition additional ray collectors.

Parabolic or “point-focus distributed receiver” With the highest concentration factor of 3,000, these provide the highest efficiency. The receiver is placed at the focus. These are roughly three meters tall, and they are expensive compared to the linear concentrators. At the Sandia Test Facility, each receiver has 75kW total power each, and are used for more than power generation, including simulating re-entry vehicles from space and optical telescopes for astronomy. Below are two photos that demonstrate the two of the three types of solar collectors. The first is a solar focusing, and the second is a point focused or parabolic receiver.

The Promise of Phase Change
So far, no change of phase materials have been commercially viable (Sandia labs).A phase change is a change of state, such as a liquid to a gas. Phase changes provide great potential, because there is large energy storage in the bonds from one stage to another. For example, Air conditioning and refrigerators typically use phase changes, liquid and gas work in tandem. However, molten salt reactors would use solid-liquid have two serious problems. First, there are big problems in clogging if temps decrease past the freezing point, and currently problems outweigh advantages
 * 1 lb of water warming 1 degree is 1,055 joules (1 BTU).
 * 1 lb of ice melting is 14,470 joules or 14 BTU’s
 * Represents a 14x increase in energy storage.

Without phase change, temperature difference is key
The best liquid choice would have the largest temperature range. The greatest difference in temperature between T1 and T2 has the greatest effect. Most liquids break down or present energy challenges at high temperature required for maximum efficiency. This heat is stored by a substance that has a liquid with high heat capacity. A liquid is necessary because it must flow. Oils (hydrocarbon) were used in preliminary designs in solar concentrated power. In Spain and Sicily, the operational solar concentrate plants use oil successfully as a heat transfer medium. By definition, oils are long chains of methyl groups. The advantages are that oils are cheap, liquid at elevated temperature, and non-corrosive. The disadvantages are that oils breaks down into gasses and fails at higher temperatures (above 500 F), and since high temps cannot be reached, lowers efficiency. This increases storage capacity requirements and costs. In addition, oils are flammable and explosive. Molten salts provide an alternative to oil transfer mediums. A molten salt is defined when an ionic solid, such as sodium chloride (table salt). But, there are many ionic salts, and two additional types are sodium nitrate, also known as saltpeter, NaNO3 and potassium nitrate, KNO3. Both of these materials are solid at room temperature and have common uses in many applications from gunpowder to fertilizers.
 * **Substance** || **Heat Capacity (J/gram)** ||
 * Water || 4.814 ||
 * Oil || 1.7-2.1 ||
 * NaNO3 || 1.16-1.67 (62oC-337oC) ||
 * KNO3 || 0.97-1.39(62oC -457oC) ||

Molten salts are good under pressure
Advantages of molten salts are low costs, are liquids at high temps, and operate at low pressures (near 1 atmosphere or 14.7 psi). Water which is raised to over 1000 F has a pressure of over 400kPa or roughly 26,500 psi. The burst pressure rated for the highest quality stainless steel pipe is 28,000 psi, and the maximum working pressure of the same type of pipe is 10,500 psi. Designing and engineering a plant working at such pressures has enormous engineering challenges to ensure safety, but it is much easier to design a plant that operates near ambient pressures.

Carnot cycle
The Carnot cycle is defined as:

This cycle predicts the maximum efficiency of an engine based on the temperature change. Below in the table include some of the operating temperatures of the transfer methods. C (Kelvin) || Max Operating Temp F/C /(Kelvin) || Maximum Carnot Efficiency ||
 * **Carnot Cycle Efficiencies** ||
 * || Lower Operating Temp
 * Water || 150 (288K) || 1050o F/565o C/(838K) || 39% ||
 * Oil || 20o (293K) || 400 o F /200o C(473K) || 38% ||
 * KNO3, NaNO3 mixture || 290o (563K) || 1050o F/565o C/(838K) || 33% ||

As discussed earlier, water presents large challenges for a molten salt reactor. Oil has an operating temperature that is relatively low. Although the operating temperature ranges are similar, concentrated solar have temperatures near 5,000 F, which lends itself to a transfer fluid that can reach high temperatures. Temperature difference is also key in transferring the energy from one source to another. Surface area energy transfer, “rate of energy transfer due to a temperature difference”

There are disadvantages to molten salts. They are corrosive and wear down the pipes at a gradual rate, and they are solid at room temperature. In large quantities they can be toxic, and given the right conditions, they can be a fire hazard. The latter presents engineering problems.

General properties
Modeling liquids have additional challenges. They are difficult to model compared to gasses. In a gas model description, particles rarely come into contact with each other, are treated as elastic objects, and the attraction between particles is ignored. In a solid model description, particles in a solid are fixed distances from each other, have unique geometry that gain insight such as body centered cubic BCC, and face centered cubic FCC. The attraction between particles is a dominate feature. Liquids have features of both solids and gasses. Modeling liquids are not covered in most introductory texts, and the best successes with computational modeling and computational methods. Laminar flow, an idealized case, requires hefty differential equations to model, and that ignores many of the interactions of the materials. Physical properties allow for insights that allow for liquid behavior insights. The melting points of NaNO3 and KNO3 are high, near 3000 Celsius, and the structure of the liquid is ionic. Both NaNO3 and KNO3 are poor conductors as a solid, but are good conductors as salty aqueous solutions. While they are not as a good as a conductor as metal, they retain must contain some ions to conduct current. The structure of liquid can be discerned by examining the notion that molten salts can conduct and by careful analysis of the entropy of the phase change. Since molten salts conduct, the liquid is full of ions. But how are these ions arranged? Coulomb’s law suggests that the positive and negative ions will maximize their relative distance, but are these ions arranged randomly? Entropy is the measure of probable disorder in a system. A small change in entropy suggests a small change in the overall pattern or atomic structure. Any substance that melts will undergo some entropy change because the orderly crystalline structure will be dismantled. The question then is how much is the disorder compared to the parent elements? By examining the entropy change of melting NaNO3 and KNO3 they represent an entropy change that is at least one order of magnitude less than the sodium or potassium metals. This suggests that they maintain structure even in liquid form. Because they have structure at the liquid state, it explains the low volatility of the salts and why they remain liquid at room temperature. They still have some structure in a coherent way compared to their parent elements.
 * || **Na (Sodium) Melting** || **K (Potassium) Melting** || **NO3 (Nitrate) Melting** || **NaNO3 melting** || **KNO3 melting** ||
 * Entropy change || 139 || 155 || Unable to determine || 8.4 || 13.8 ||

Conclusion
Alternatives to fossil fuels need to be explored because they are dwindling in supply and this presents and economic and national security issue. Solar energy is a renewable resource and some of the major challenges of power generation and supply have been overcome. Challenges remain in the distribution of the power, but maintaining power in a 24 cycle has a reasonable engineering solution. Molten salts provide an alternative to other transfer liquids such as oil and water. Molten salts can reach high temperatures and their heat capacities increase with temperature, but they also keep liquid at ambient temperatures, solving significant engineering challenges. These advantages are revealed =References= Carling, R. (1983) “Heat Capacities of NaNO3 and KNO3 from 350K to 800K” Thermochimica Acta, //vol 60, issue 3, p. 265-// //275// Energy Information Agency (2011) “Concentrated Solar Potential” Retrieved from: [] Energy Information Agency (2011) “Shipments of Reactors” Retrieved from: [] Ivanov, V.A. (1973) “Thermodynamics of melting sodium at high pressures” Physics Letters A, //vol 47, Issue 1, p. 75-76// Pimentel, G., Spratley R. (1969) __Chemical Bonding Clarified Through Quantum Mechanics__, Holden-Day, Inc. ISBN: 0- 8162-6781-2 Sandia Laboratories “Advantages of Molten Salts” Retrieved from: [] Sandia Laboratories “Desirable Features of Power Towers for Utilities” Retrieved from: [] Tallon, J. (1980) “The entropy change on melting simple substances” Physics Letters A//, vol 76, Issue 2 p. 139-142// Wikipedia (2011) “The British Thermal Unit”. Retrieved from: [] Wikipedia (2011) “Energy in the United States”. Retrieved from: []

 An I-Phone 4 has a mass of 4.8 ounces or 140 grams.  This is misleading: if everyone is home and major appliances are working, then the home can easily use 5,000 watts. If an air-conditioner and a clothes dryer are working simultaneously, power requirements can reach 10,000 watts.