kW and kWh Explained - Understand & Convert Between Power and Energy
Answer to 1. What is the relationship between kWh and joules? explain briefly 2. Exoplain briefly the differences between peak an. You should be able to calculate the cost of using an electrical appliance when given enough information about it. One unit is 1kWh. The equation below shows the relationship between energy transferred, power and time: Units ( kilowatt-hours) are used instead of joules because a joule is a very small unit of energy. The relation between kilowatt hour and joule is.. 1 kWh = JAnd 1 kWh = 3·6 MJ (mega joules)Hope it will help you:)Thank you.
It is a rate.
To use an automotive analogy, it is equivalent to how fast you are driving. If you lift a can of soda to your mouth in one second, then you are exerting one Joule per second, also known as one Watt, of power. One thousand Watts is one kilowatt, abbreviated kW. If you use one kilowatt of power for an hour, you have used 1 kilowatt-hour, abbreviated kWh, of energy.
One kilowatt-hour is equivalent to the energy of 1, joules used for 3, seconds or 3.
So if your building uses kWh each day, your building is consuming the same amount of energy that would be required to lift 18 billion cans of soda per day. At the moment, fossil fuels are the major source of energy for power generation across the globe. However, greenhouse gas emissions, which they cause, contribute to global warming.
An additional problem with fossil fuels is that they are not renewable and are being depleted faster than the new fossil fuels are being created. If we mostly rely on fossil fuels, we will one day run out of energy sources. Cooling towers of a nuclear power plant.
Image courtesy of RF. It is generated through a controlled nuclear fission reaction,where a nucleus of an atom splits into smaller parts and releases energy. The energy heats water and produces steam, which, in turn, moves the turbines. It poses safety concerns, especially after a number of nuclear power plant accidents, the most infamous and disastrous being the Chernobyl one in Ukraine, Three Mile Island one in the USA, and the Fukushima one in Japan.
After the Fukushima disaster, a number of countries started to re-evaluate their use of nuclear power, and some, such as Germany, are now working on closing down their nuclear power plants in the near future. An additional problem is the storage of spent nuclear fuel. Fuel is needed for the fission reaction to occur, and it can be reused, but eventually it has to be replaced. Some of the byproducts of nuclear power production can be reused in other industries such as medicine or weapon production, but most of the material has to be stored as radioactive waste.
Currently each country has their own storage systems for the spent fuel. They include repositories in geological structures or the ocean floor, as well as storage in spent fuel pools or casks. This poses problems and risks such as costs, leakage, running out of storage, and hostile attacks on the storage facilities. Pickering Nuclear Generating Station, Ontario, Canada A safer alternative that is currently being researched is to produce power from nuclear fusion, a reaction that releases energy when several nuclei collide at high speed and join into a new nucleus.
This happens because when two nuclei are at a very close proximity to each other, the forces that repel the nuclei are weaker than the forces that attract them together.
Similar to nuclear fission, this reaction produces radioactive waste, but this waste will cease to be radioactive after about one hundred years, compared to thousands of years with nuclear fission. The materials needed to produce this reaction are also less costly. At the moment, fusion reactions require high amounts of energy to facilitate, but researchers are working on ways to make this reaction produce more energy than it requires and make it economical.
Renewable Energy Other alternatives include using renewable power sources, such as energy from waves, sunlight, and wind. At the moment these alternative sources are not developed enough to replace fossil fuels. However, thanks to the subsidies provided by some governments, and also because these energy sources are much less harmful to the environment than the non-renewable ones, they are becoming more and more popular.
Photovoltaic panel Solar Energy Solar energy experiments started inbut this technology was not widely used until recently. In recent years, solar industry is developing very rapidly due to demand and subsidies from governments and international organizations. Solar farms, which are large areas covered with solar panels, were first built in the s. Most often solar energy is collected and electricity is generated by means of photovoltaic panels.
Sometimes heat engines are used in which solar energy heats water and resulting water vapour rotates the turbines, which in turn rotate generators. Wind turbine at the Exhibition Place. The first major use was in sailing, as far as years ago. Windmills have also been in use for hundreds of years. The first wind turbines were created in the s. Marine Energy Tidal energy has also been used since the time of the Roman Empire, but the energy of waves and currents has only been used recently.
In recent years stations that harvest wave, tidal, and current energy are being built and tested. While the idea of generating energy from marine power is not new, devices that harvest this energy on a large scale need to be further developed and tested. This is mainly due to high costs of building such power stations, and to the lack of advancement in current technologies. Marine energy has a great potential to provide energy for large populations. During this process solar energy that plants generated through photosynthesis is released as heat.
It is widely used in everyday life, for example to provide warmth for heating and cooking, and also as fuel for transportation. Alcohols and oils can be made from plants, and animal fat-based biofuel is also in use. One variation of biofuel, biodiesel, is used in the automotive industry both as an additive to other diesel fuels, or by itself.
Geothermal Energy The Earth stores energy in its core in the form of heat. Until recently, this energy has been accessible mostly in the areas that lie around the borders of tectonic plates, where hot springs are present.
Now, geothermal wells are created to have access to this energy more widely. This is a costly process, however. Niagara River near The William B. Rankine Generating Station, which was closed in Hydro generated power is considered by many to be clean energy with little negative environmental impact.
Indeed, with this energy source greenhouse gas emissions are not a problem as they are for fossil fuels.
Hydroelectric energy is generated by water flow. It has been in use by humans for a long time. A watermill is one example of using this energy.
Currently, electricity is generated by harvesting kinetic energy of flowing water of rivers, or potential energy of water in reservoirs. This energy moves water turbines. The dams use the height difference between the reservoir from which the water flows, and the river into which the water flows. Lewiston, New York, United States Despite the positive aspects of hydroelectric energy, numerous problems exist with its generation. For example, displacing and damaging habitats when building dams causes considerable harm to the biodiversity.
Provided it has the optimum level of wind which probably doesn't happen nearly as often as its owner would likeit can generate 10 kW of power. How long does it take to generate 10 kW? That's a question that would only be asked by somebody that didn't understand what power was. It's a bit like asking "how long does it take to travel 10 miles per hour? The two are closely connected, but we'll get to that shortly. Things that "use power" Items of electrical equipment like light bulbs, computers, and fans, take energy in the form of electricity, and use it to do useful things for us.
Really they're converting the energy into other forms heat, motion etc. The rate at which these things use energy is their power. Or, depending on the thing, and the person you're talking to, you might hear it called their "load" or their "demand", or you might just hear it referred to in terms of a W or kW value.
Light bulbs are a simple example: The watts aren't affected by how long the W light bulb is running for A second, an hour, a day - no difference - so long as it's switched on it will be using W of power.
If it's not switched on it won't be using any power i. Some equipment is more complicated.
It depends on what it's doing - if it's sitting there doing nothing it'll probably use less power than if you're hammering away on an Excel spreadsheet, listening to some music, and burning a DVD, all at the same time.
We make a distinction between instantaneous power and average power: Instantaneous power The instantaneous power or instantaneous demand, or instantaneous load is the power that something is using or generating at any one moment in time. Put your laptop on standby and its instantaneous power will drop immediately. Bring it back to life and its instantaneous power will rise immediately. If, at any particular moment, everything in an office building is switched on, that office building might be using 42 kW of power.
That's 42 kW of instantaneous power.
BBC - GCSE Bitesize: The cost of using electricity
If, at any particular moment, everything in the office building is switched off, that building should be using 0 kW of power. That's 0 kW of instantaneous power. The instantaneous power of most buildings varies constantly. People are constantly switching things on and off, and many items of equipment within the building have instantaneous power that is constantly changing too. Average power The average power represents the power that something uses or generates, on average: Remember our example of an office building that uses 42 kW of power when everything's switched on, and 0 kW of power when everything's switched off?
If, on average, half the things in the office building are switched on, and half are switched off, then the average power will be around 21 kW overall 21 kW being half of 42 kW. Or maybe that's just the average power of the office building on weekdays. On weekends, when people are at home, and most equipment in the building is switched off, the average power might be lower, maybe 5 or 10 kW.
Average power enables you think of complicated things, like buildings, as if they were simple things, like light bulbs The instantaneous power of a typical building varies all the time.
If you try to monitor instantaneous power you get lost in the noise. And figures of energy consumption are meaningless unless you know the length of the periods that they were measured over. But average-power figures smooth out the constant fluctuations of instantaneous power, and make it possible to compare the efficiency of different periods, like for like, without worrying about how long those periods were.
The building used 41 kW on average across the whole of last week. The building used 19 kW on average across all the Saturdays and Sundays since March We don't need to care how many Saturdays and Sundays there were since March The building used 38 kW on average between That's double the average kW of a typical weekend, and that's bad because 3rd May was a bank holiday and the building was closed.
You can easily use these average-kW figures to compare the energy consumption of different periods and even different buildings we use the term "energy consumption" loosely because really we're talking about average power, not energy. It's a bit like comparing the fuel consumption of cars: On long journeys my car does an average of 45 miles per gallon. My brother's car does an average of Around town my car does an average of 32 miles per gallon.
These average-mpg figures would typically be calculated across multiple different journeys, each covering different distances But you can compare the figures like for like, without worrying about the details of the specific journeys that they were calculated from. Average power works in the same way, but with energy instead of distance. In many ways average-kW figures are easier to work with than kWh figures.
To remove ambiguity we might call it "average power", or "load", or "demand".