1. INTRODUCTION: FUTURE ENERGY NEEDS

Mankind has recently enhanced its living standard and its population in an explosive way. In fact, the human population quadrupled and primary power consumption increased 16-fold during the 20th century [1]. The consumption of energy, food, and material resources is predicted to increase 2.5 fold in the coming 50 years. As a result of our efforts for better life, we have come to face, in this 21st century, serious global issues threatening our safe life or even our existence itself on our mother planet earth. These are issues such as global warming, environmental degradation, declining nutrition on land and sea from rising CO2, and rapid decrease of fossil reservoir. Since the living standard and the population of developing countries are increasing continuously, the demand of energy will be several times larger than that of today’s requirement by the time of the half way of this century.

In 2000, the world had 6.1 billion human inhabitants. This number could rise to more

than 9 billions in the next 50 years as shown in Fig.-1. This future population increase is mostly due to very rapid increase in less developed countries although the number in more developed countries will be almost constant (about 1 billion) or rather decrease [2].

Fig.-1 World Population Prospects [2]

The explosive increase in the human population inevitably requires an exponential increase in the consumption of energy, food, and material resources. One primary power source at present comes from fossil fuels such as oil, coal and natural gas. However, the fossil fuels have two serious factors which prevent them from being used for a long term as primary power source. One is their limited amount that does not last long if used with the same or higher pace than that of today (Fig.-2). The other is their negative feature of emitting carbon dioxide, one of the green house gases, which causes the global warming.

Fig.- 2 Pattern of Global Energy Dependence [3]

Fig.-3 Atmospheric carbon dioxide monthly mean mixing ratios. Data prior to May 1974 are from the Scripps Institution of Oceanography (SIO, blue), date since May 1974 are from the National Oceanic and Atmospheric Administration (NOAA, red). A long term trend curve is fitted to the monthly mean values [4]

Atmospheric CO2 has increased from 275 parts per million (ppm) before the industrial era begun to 379 ppm in March 2004 as shown in Fig.-3. Some scientists suggest that it will pass 550 ppm this century. Climate models and paleoclimate data indicate that 550 ppm, if sustained, could eventually produce global warming comparable in magnitude but opposite in sign to the global cooling of the last Ice Age [5].

Global energy demand continues to grow along with worldwide concerns over fossil fuel pollution, the safety of nuclear power and waste, and the impact of carbon-burning fuels on global warming. As a result sustainable energy sources like solar, wind, hydropower, biomass, geothermal, hydrogen, ocean thermal, tidal power etc are drawing prime attention, out of which solar power is the most promising one. Terrestrial solar power has too many limitations like atmospheric attenuation, daily and seasonal variation, and affects by climate conditions etc. To overcome these limitations concept of Solar Power from Space is getting momentum, which was first proposed by Czech-American engineer Peter Glaser as a solution to the oil crises of the 1970s [6]. Solar Power from Space is a proposed concept to place a gigantic solar power station in space orbiting around the earth that uses microwave power transmission to beam solar power to a very large antenna on earth where it can be used in place of conventional power sources.

2. SPACE SOLAR POWER (SSP) vs TERRESTRIAL SOLAR POWER (TSP)                   

The SSP concept arose because space has several major advantages over earth for the collection of solar power. Space is free from day-night cycle, atmosphere, clouds, dust, rain, fog and other climatic changes, so it would receive 30% more intense and at least eight times more sunlight than that of at ground constantly and continuously unaffected by the weather. In geosynchronous orbit it would receive sunlight almost 24 hours a day hence avoiding the expensive storage facilities necessary for earth-based solar power systems.  Since earth’s axis is tilted, it would be in earth’s shadow only for 70 minutes maximum at late night when power demands are at their lowest, during 42 days near the equinoxes [7] as shown in Fig.-5.

Fig.-5 Daily duration of eclipses as a function of the date [7]

3. SSP: SYSTEM DESIGN AND TECHNOLOGIES

The SSP system is composed of a space segment and a ground power receiving site (Fig.-6). Space segment consists of mainly three parts; solar energy collector to convert the solar energy into DC (Direct Current) electricity, DC-to-microwave converter, and large antenna array to beam down the microwave power to the ground. Ground power receiving site uses a device called rectenna (rectifying antenna) to receive and rectify the microwave power beam. The rectenna system converts the microwave power back to DC power which is then converted to conventional AC (Alternating Current), and is connected to existing electric power networks.

Assuming typical values for efficiencies like 15% for solar panels to convert solar energy into DC, 70% conversion rate in the space segment from DC to microwave, 90% beam (power) collection efficiency, and 80% conversion rate for rectenna from microwave to DC in ground segment, the estimated over-all efficiency is approximately 7.5 %. With such efficiency a SSP space segment would be of size of about 50 km2 (5 km x 10 km) to generate 5 GW DC power on earth (Fig.-6).

Fig.-6 : Reference Model: 5 GW GEO based Space Solar Power Station Designed by US Department of Energy (DOE) and NASA in 1979 [8]

3.1 -SOLAR CELL: EFFICIENT STRUCTURES

In the very near future, breakthroughs in nanotechnologies promise significant increase in solar cell efficiencies from current 15% values to over 50% levels. That might decrease required size of space segment by about 3 fold. Author proposes Metal-Metal junction cavity solar cell which theoretically promises to increase solar-electric conversion efficiency many folds.

A cavity of metal m2 (work function W2) with thin polish of metal m1 (work function W1, W1 <W2 , Fig.-7) on inner surface, with a pin hole is kept at the focus of the solar concentrator coinciding the pinhole and focus. Pinhole is covered with transparent glass to protect inner polish of cavity from atmospheric reaction. Such cavity behaves as metal-metal junction solar cell (termed as M-M cavity solar cell) with various features (described below) leading to enhancement of solar-electric conversion efficiency.

·  The major loss in usual structures is the reflection loss (about 30%) but in M-M cavity solar cell once ray enters in cavity, undergoes multiple inner reflecti

s.sankar
http://www.articlesbase.com/cell-phones-articles/energy-compensation-using-solar-power-stations-in-space-685742.html

Solar power is generated when energy is extracted from the suns rays through the use of photovoltaic cells (commonly referred to as solar cells). These cells convert photos (from the suns rays) into electricity, and this process is known as the “photovoltaic effect.”

Many people are beginning to invest in such technologies to avoid rising electricity prices and to help our environment. If every home could be fitted with solar panels, then the strain on power stations would decrease dramatically, which means we wouldn’t be left as dependable on fossil fuels as we currently are.

There are many alternatives to solar power, so why should we invest our money into solar technologies, rather than lets say, home wind turbines, or a geothermal energy system? To answer this, we shall look at the advantages and disadvantages of the technologies above.

Solar Panels:

Advantages - widely available, relatively easy to install, very significant output, a solar panel will pay for itself in two to three years, lifetime of 20 to 30 years, modern cells can harness power on cloudy days, can bring power to remote locations.

Disadvantages - costly to begin with, older technologies won’t work too well if cloudy.

Wind Turbines:

Advantages - fairly cheap for a home turbine, can be used in harsh conditions.

Disadvantages - totally dependent on the wind, small output, larger turbines can be noisy, wind farms are seen by many as eyesores, larger (more effective) turbines can be very expensive.

Geothermal Energy:

Advantages - can aid in the heating of hot water, save money on running your boiler, can supply effective underfloor heating, heat from the ground can be relied upon.

Disadvantages - have to lay hundreds of meters of piping underground, hard to fix a leak, expensive, longer time to heat water than a boiler.

So there we have the advantages and disadvantages of each. Assuming you do not live by a rapid stream or running river (which rules out hydroelectric power), then as you can see from the above text, solar power is your best option. Solar panels offer many more friendly factors and less disadvantages than other technologies.

A proven method is to have more than one of the above technologies installed around a home (all three would be a dream, but also leave a large hole in your wallet). So if you have the spare cash, are interrested in saving money on future electricity bills, care for the environment, and would like to be less dependent on fossil fuels, why not take a deeper look into the world of renewable energy resources.

http://www.clean-energy-ideas.com/solar_panels.html

James Bratley
http://www.articlesbase.com/environment-articles/solar-panels-power-your-home-for-free-106007.html

People have been aware that the sun’s energy can be harnessed to power various devices and machines for years, but it is not until recently that the technology and the motivation has pushed people to seriously consider solar energy as a viable power source.

With the current state of the economy and with the growing move toward a more environmentally responsible lifestyle, many people are considering various forms of renewable energy and “green living” principals. Solar power is usually at the top of the list when it comes to renewable energy sources. Solar power has been used for years by the government and various businesses, but it has only recently come into the mainstream for the everyday average household.

In almost any area of the country it is possible to dramatically cut one’s electric bill by installing and maintaining solar panels. Some people are even able to go entirely off the grid and power their homes completely independently of the traditional local electric company, all by solar power. While going off the grid may be an intimidating prospect for some, there is absolutely no reason why a household cannot install solar panels on the roof and greatly reduce the monthly electric bills.

Until recently, the cost to buy and install residential solar panels has been prohibitively high, and not everyone has the technical know how to do it themselves. However, with the shift toward renewable energy, many companies have seen this as an opportunity in an untapped industry and have started offering solar panels at much more competitive and affordable prices. The installation and upkeep of the solar panels is very easy and affordable. Many households find that they can pay for the solar panels in less than a year through the reduced electric bills they produce.

Obviously, once the panels are installed, the solar power is completely free and produces absolutely no harmful emissions, unlike traditional fossil fuels. As the technology becomes more mainstream, manufacturers and builders are constantly refining their techniques to make the solar panels more efficient, durable and innovative.

Recently, some builders have started to integrate solar power into their overall design by including solar panels as standard features on top of garages and in other unobtrusive places such as the roofs of gazebos, tops of pool houses, and on every available foot of roof space in general. Some pool decks are being built with embedded solar cells. As the renewable energy movement continues, more and more builders will find it necessary to integrate a solar power plan into their overall building plan in order to stay competitive with all the other builders who are doing the same.

Solar power is one of the easiest and best solutions to not only help the environment and climate, but to save significant amounts of money in electric bills as well. With solar power components being more affordable now than ever before, every homeowner should at least consider installing solar panels.

David J Hughes
http://www.articlesbase.com/home-improvement-articles/renewable-energy-lesson-2-solar-power-754985.html

Today, it is easier than ever to build your own Solar Panel, with all the kits and methods available, your own homemade solar panel can be an effective way to produce your own power and save on future power bills. All the components required for creating your own solar panel are made available in most kits. These components typically include: solar cells, a soldering iron, flux and tabbing. Kits typically include detailed instructions on how to make a solar panel. Constructing a solar panel at home does not require professional expertise. All you need is a kit, guideline, clear idea and a logical mind. You can simply follow the step-by-step instructions available with the kit and create you very own homemade solar panels.

Homemade solar panel can be made from a collection of solar cells. Each solar cell produces a small amount of electricity, but collectively they can produce enough electricity to fulfill your household power needs. It is important for the panels to keep facing the sun to receive direct sunrays. It’s the crucial requirement for its working because again our logical mind says that the sun is the source of energy for our solar panels so it should not be barrier by shade or not-so-ample sunlight. There must be no hurdle between sun and solar panels, the way should be clear and direct.

You can choose from a number of tracking solar mounts available. The single-axis tracker is fixed at a vertical angle. The angel is manually maneuvered to follow the path of the sun, which is based on seasonal changes. For summer, the rule of thumb is to set the panels at your latitude minus 15, and for winter, you can set the panels at your latitude plus 15. The dual-axis tracker adjusts the vertical angle automatically. So you don’t need to worry about that either. It works easily and efficiently without any extra care and maintenance.

Biggest advantage of building and installing solar panel is that they are eco-friendly. They produce green energy to use the latest terminology. Other forms of electricity emit certain harmful elements that contribute to smog, and other pollution, while solar power is free from such perilous emissions. If you find you entail more energy output, you may add more solar panels to generate more power. At the end of the day it all depends on your own requirement of energy so you can adjust your solar panels accordingly. There is no hard and fast rule in the amount of panels, they more you want you can add to your roof with proportion to the space available.

pratibha
http://www.articlesbase.com/home-improvement-articles/homemade-solar-panel-678070.html

Are you planning to ‘Go Green’ and add a solar power to your home? You have made a wise decision but first, you need to know that there are benefits and drawbacks to adding a solar power system to your home. I will cover them both in this article.

First a few of the benefits. Solar power will help to;

• reduce or even eliminate your electric bills
• increase the value of your home
• decrease dependency on foreign energy
• help the earth by creating completely ‘renewable’ energy
• reduce pollution and leave a better planet for our children and grandchildren

As for the drawbacks for solar power which can be very expensive, many commercially made systems are incredibly high price. You could be forced to take out a second mortgage on your home. Commercially made solar system has to be installed and the install fee is high. Hire your own contractor to do the work is not only expensive, but time consuming and could disrupt your home for months.

So why invest for a commercially made solar power generator while you can ‘Do-It-Yourself’ in just one week time for less than $200. If you are as ‘DIY’ challenged as I am you can build one for yourself. With these simple instructions (written in plain English but not constructionist directions) anyone can learn to do this and it is a fun weekend project and you can get the kids involved. You have probably seen or heard about solar energy system on television or internet, why? Because it works!

Let me show you how to successfully create a solar system for less than $200

Jonathan Valentine
http://www.articlesbase.com/diy-articles/earth-4-energy-build-your-own-solar-power-system-695597.html

Two solar power technologies exist, the passive and the active technology. The passive technology are the photocell panels or the photovoltaic film that receives sunlight and generates electricity more apt for a space station or a home. The active technology is a solar thermal that uses a dish to concentrate sunlight that produces steam, which in turn powers a turbine that generates electricity. Another active technology, which is not being promoted, hidden form public view, is using the Stirling Engine to move a power generator.

The passive technology is ready to go, and there are a few homes that have already installed the system. This system is totally clean, backed by the USDOE Solar American Initiative, it requires sufficient space on the roof to position the panels or film, and uses an inverter to turn direct current into alternate current homes can use. The Utility companies have also developed the Net Metering system to buy electricity on their terms, from homes that have generate a surplus of electricity. The new federal tax law “Emergency Economic Stabilization Act of 2008″ effective January 2009 provides a 30% tax credit of the cost of a solar system. Some States are also providing large incentives to install solar systems, although with the current economic crisis these paybacks can be curtailed or delayed. The rest of the payback has to come from real savings generated over time by the system from the Utility company. This passive solar system is expensive as of today, and payback is obtained in 8 years of savings. Photovoltaic film or photocell panels are low efficiency and voltage, and compare badly with the option of buying electricity from the utility company. Currently you require from 13 to 15 photocell panels to generate the 2.5 to 3.0 Kilowatt hours generating capacity.

Walmart has established a pilot plan to install photovoltaic panels in several of their stores. If the system produces a return, they will massively implement it in all their stores, since they have sufficient roof space currently not utilized.

The Solar-thermal system is not adequate for homes and mainly will be used for large Utility companies. However, the active system based on a Stirling engine to power a generator which could be applicable for homes, is not available for massive distribution. Although all of its components have been developed, no one has yet integrated the solar power generating kit, or a home appliance. This home system or appliance should be very low cost because it requires: a solar collector or dish which could cost around $200 USD, a stiriling engine with a cost of $350, the 3 KW per hour power generator with a cost of $350, and the battery bank which is the expensive ticket item and could run several thousand dollars, to store electricity if the system is a stand alone not tied to the power grid. If the home is currently supplied by a utility company, then the battery bank is not needed and the Net Metering system with the public utility company can be used. In addition to the sun collector dish the rest of the system can be packaged in two boxes. One which has the stiriling engine and power generator, and the other with the battery if you are a location not tied to the grid. It can also have a gas heater installation as a backup to when there is a lack of sunlight making this a very reliable alternative.

Apparently, there are companies in America, New Zealand, India, Sweden, and other countries trying to develop the stiriling engine . A few companies are receiving funding from investment funds to develop the stiriling engine for this home appliance. Infinia Corporation, a US company has a head start, because they are currently producing a big sterling engine to power up 10 homes at a time and installing many of them in a centralized solar farm in California. Other companies should not be discouraged because markets are so huge, there will be enough room for all suppliers. Just in United States alone there is a potential of 124 million homes that could use the solar power appliance, plus commercial and industrial sites.

Having the home powering appliance, can be the initial steps for returning to sustainable systems. Today, the sun is light and warmth, provided to us from God and Nature, free for all of us to use and enjoy. A home solar powered generator would provide clean energy, and allow equal footing to all nations rich and poor, to devote their funding into other worthwhile social services such as health and education. Rich nations which have electrical grids and power generation capacity would suddenly feel there would be no need to continue increasing Power generation capacities and hopefully they would discontinue all those plants that contaminate. Please see Poverty generation:  http://www.articlesbase.com/politics-articles/poverty-and-the-new-world-order-809385.html

Juan Trevino
http://www.articlesbase.com/environment-articles/solar-power-technologies-on-hold-673269.html

Solar energy is a great renewable resource that is growing in popularity with the average consumer. As energy prices skyrocket and the average income stagnating, if not falling, consumers are looking for a way to reduce their costs of living in any area possible. The rise of renewable energy, and the desire to wean our society off of fossil fuels, makes using solar panels for the home a great alternative for power.

Solar power kits save energy for the homeowner because they allow the homeowner to generate their own electricity to power their home. In some cases, the homeowner can go completely off-grid and even sell additional electricity back to the power company. What a powerful concept to be able to take an expense and turn it into an asset.

What are solar panels?

A solar panel is a packaged interconnected assembly of solar cells that are cased in a housing unit to protect the cells from the weather and from physical damage. These panels generate electricity, which is then used to directly power devices in the home, or charge battery cells to store the power for nighttime use. A solar power kit typically includes solar panels, an inverter and interconnection wiring to connect the panel to the electrical system in the home. For those that want to live off the grid, batteries are included for continuous power during the day and night. The use of infrared solar cells also allows the homeowner to generate electricity at night, thus increasing the efficiency of these cells.

The technology of solar cells continues to advance with time. Currently, the efficiency rate of solar cells range from 5% to 19% depending upon the technology. The reason is that the solar cells (or photo-voltaic cells) only convert a limited range of sunlight frequencies into electricity. The renewable energy industry is experimenting with advanced technologies that will raise the efficiency of these solar cells by a whopping 50%.

A new technology for solar cells, also called thin film or third generation solar cells, is being researched. The plus side of this new generation technology is that it produces solar cells that can operate with a higher efficiency and less cost. These brands are both rigid and flexible thin film modules. The differences between the rigid thin film module and the flexible thin film module are due to differences in the materials that are used to make the modules and differences in the production of the modules.

Solar modules can last anywhere from 10 to 25 years while still operating at 80% of their original capacity. Every year the number of panels sold to consumers continues to grow. In 2007 over 4 million solar units were sold. There are a number of manufacturers that produce solar panels for consumer use, however the average consumer can create their own solar panels using materials from their local hardware store.

Solar panels for the home can provide renewable energy for the consumer. The initial costs can range greatly if the consumer chooses to build their own solar energy kit or have another company install a solar power kit. As the technology improves, the homeowner will have more options available to them to completely power their home with renewable solar power energy.

B Hopkins
http://www.articlesbase.com/internet-articles/what-are-solar-panels-for-the-home-710880.html

 

How would you like to reduce your dependency on fossil fuels? How would you like to decrease your reliance on the power companies and cut the size of your bill each month? If you answered yes to both of these questions switching to solar power will greatly benefit you. PV systems make advantage of the suns rays and convert them into usable source of energy. The sun offers a renewable, and barring any unforeseen events, a timeless source of energy. Solar power is both financially and environmentally friendly. By using solar power one can save money, and reduce the amount of greenhouse gases in the atmosphere that are released through the burning of fossil fuel and natural gas for power. 

 

When considering electrical bills, switching to solar power has become the oblivious answer for many people and their households. Electrical bills make up a large portion of the household budget, and during the winter months they account for half of the power bills spent in a home. A solar power system is the one way to reduce or even eliminate your electrical bills.

 

Having your home run on solar power is easy to do, and many resources make installation an easy to do it yourself process. First consider a budget for your solar power spending; this can be based off of how much of your home you will power to solar energy, or the amount of kilowatt-hours your home uses. Once you purchase the basic parts: solar panels, inverter, battery, wires, etc, installation is easy. 

 

The solar panels which will be ground or roof mounted will provide the DC current which will be taken by the inverter and transformed into AC current which will be used to power your home. One key advantage of solar power that has attracted many is its longevity. Besides the sun providing a constant source of energy, solar panels are extremely durable. Solar panels can function for many decades before showing signs of failures, so if you are on a tight budget you can purchase used solar panels worry free. Solar power is an obvious answer to reducing dependency on fossil fuels and thus power companies. The process is inexpensive, and easy for a person to do themselves.   

 

 

MejI Alabi
http://www.articlesbase.com/diy-articles/solar-power-is-easy-do-it-yourself-684650.html

The simple fact is that we cannot depend on oil and fossil fuels for our energy forever. Many people are already starting to realize this and are beginning to switch to residential solar power.

Using residential solar power may seem complicated but it’s simpler than you might think. I personally know people that aren’t as smart (or as good looking) as you and they have built their own solar power system.

First, let’s talk about what solar power is and how it works.

Solar power is an amazing thing. The sun blasts more than enough energy to provide us enough power to sustain ourselves. They key is being able to harness this energy and use it to our benefit. Our goal is to take this energy and convert it into electricity. Once we convert to electricity, this will give us all the residential solar power we will ever need.

Electricity is created by solar panels and converted using photovoltaic cells. The word photovoltaic literally means ‘light electricity’. Don’t let these big words confuse you, creating solar power for homes is quite simple and anyone can do it.

A solar generator can cost as little as $200 and can pay for itself within the first few weeks that you put it into use. Not to mention the benefits to the environment.

Let me give you an example of a recent solar generator I built. This is what’s called a ‘portable solar power system’ and can be made with only four pieces of material. (solar panel, charge controller, battery and inverter) These supplies can be purchased from any major hardware store and should cost around $200 total. This is one of the most popular systems to build due to the fact that it is ‘portable’. Take it wherever you like and you will never have to worry about the lack of electricity again. With a system like this, you should be able to get your investment back in as little as two weeks.

I have cut my electric bill be nearly 85% due to the solar panels I have built. Not to mention that the whole setup cost just under $200. Now how’s that for ‘going green’.

Anyone can do this, sometimes on a much larger scale. I’ve have know people who SELL the excess energy that they don’t use back to the electric company. So much for being at the mercy of the power company. Now you can actually MAKE money from them.

The idea of making homemade solar power was unheard of 20 years ago, but today is one of the fastest growing trends in the world. With the ever increasing costs of utility bills it just makes sense for someone to use homemade solar power as an alternative energy resource.

Gen Wright
http://www.articlesbase.com/branding-articles/residential-solar-power-how-to-make-your-own-energy-718649.html

With the economic crisis the world is facing right now, more and more people are turning to solar power for electricity. The reason for this is that you can save tons of money on your energy costs. Some people are even able to disconnect from their power companies and be completely energy independent.

http://www.my-linker.com/hop/energy4earth

This is done by installing solar power energy panels on to your home. You do not have to pay a professional thousands of dollars to come out and install solar panels for you. You can do it yourself. Find a book that has detailed instructions on how to install your own solar panels. I prefer one with diagram illustrations so that it is easier to comprehend. All of the supplies you need can be found at your local home improvement store for just a couple hundred bucks. Your solar panels will quickly pay for themselves with the amount you save on electricity.

Once you have everything you need, putting it together and installing it is a simple process that can be done in just one weekend. Your home will be more energy efficient and you will be amazed at the tiny utility bills that you will start getting each month. Or, if you prefer, you can install enough solar power in your home that you no longer have to pay for electricity at all!

Not only will you be saving money, but because solar power is made from renewable energy sources (the sun), you will also be helping to save the environment. The energy that your utility company is currently using to power your home is quickly depleting our non-renewable resources. Using solar energy will help to conserve these.

Think about it. If half the people on earth that depend on the power company were to switch to their own home solar powerred system what a better situation we would all be in right now. With the recent financial crisis in America we all need to think about the coming years and how to become more self-sustainable than ever before. We need to stop polluting around the world. I strongly believe solar is weighing heavy in the start of a free energy and almost non-toxic way of living. There are of course many more ways we need to improve as humans here on earth. Our energy demands are definetly on the Top 10 list of ways to improve on.

Save the earth and your pocketbook with just a couple hundred dollars and one little trip to the home improvement store! You will be glad once you are finished and bragging to your friends and family about actually doing something to help, being part of the solution. It won’t take you long either with this guide that I used to make my own solar power sysytem. All the information is included so I didn’t have to further research any of the process from buying to building to self powerring my entire house. Good luck buiding your own home solar power system.

http://www.my-linker.com/hop/energy4earth

Shaun Bradley
http://www.articlesbase.com/home-improvement-articles/solar-power-746287.html