Υπολογισμός κατανάλωσης σπιτιού.

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αναφερει απλους τυπους υπολογισμου της καταναλωσης αλλα και της παραγωγης 
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το ανεβαζω αυτουσιο [στα αγγλικα] 

Off Grid System Sizing

A off grid installation consists of a few basic components that work together to provide you with usable power. These components are usually rated in Watts or Amp hours. How do we work out the sizing of these components? We have our power source, and this could be solar, wind, hydro, a generator or even grid power. Then we have a storage system, usually batteries. An inverter to convert the stored energy into a more versatile forum, AC. And lastly the load, what we use the power for.

There are many other components, like charge controllers, fusing, etc, but we don't need to worry about those for this exercise.




The Load. First step, and the hardest to calculate correctly, is the load. The load is how much power we want to consume, in Watt hours . To work out the Wh of an appliance, multiply the Watt rating with the number of hours it will be running during a day. Example, a 100 watt bulb running for 5 hours will use 500Wh, a 1kW ( 1k=1000 ) kettle running for 15 minutes will use 250Wh, a PC left on for 24 hours at 200 watts will use 4.8kWh !
Once you have worked out the Wh for all you appliances, total them up to get a Wh rating for the house. Less than 5kWh a day is very good, 10kWh is OK, 20kWh or more is not so good. The higher the figure, the more expensive you system will be to supply it.
Its much much much cheaper to buy a more efficient fridge, use efficient lights and turn off unused appliances than building a system to supply the extra power.
Say for example we worked out we need 10kWh a day. That's comfortable living, ample lights, TV, PC, fridge, microwave oven, using gas for cooking, solar hot water, minimal air conditioner use. Next we multiply that by 1.3 ( to allow for losses in the system ) to calculate the Wh needed from our power source ( solar, wind, etc ). So we need 13kWh from our power source.




Power Supply. We'll stick with solar for now, but the same rules apply to wind, hydro, etc. Solar panels are rated in Watts. To work out the Watt hours, we multiply the panels Watt rating by the time it's in full sunlight. For your average site, this would be about 5 to 8 hours per day, depending on the season and your place on the globe. So a typical 200 watt panel could make between 1kWh and 1.6kWh per day. We need 13kWh, so 12 to 14 panels ( 2.4kW to 2.8kW total ) should cover it at a minimum. Of course, this is assuming it never rains and we have full sunlight for every day of the year.
In reality, there may be days of cloud where our panels may make 25% of their full sun power, and we need to allow for that, either by adding more panels, reducing the load, or using alternative means of supplying power ( generator ). So it's a good idea to add as many panels as you can afford now, and set aside space to add more panels in the future. Solar panels are much cheaper than they once were, and should last for 20 or more years, so they are a good investment. You can also increase your panels output by 10% to 50% with tracking and MPPT's, but I wont go into these here.




The Inverter. The inverter needs to be sized on the total watt figure of the house at any one time. This is the peak Watts, not the Watt hours. An example may be while cooking dinner, watching TV, and ironing the cloths all at the same time. Running a iron, toaster, microwave, kettle, TV, lights and computer at one time could draw 4,000 Watts. The inverter needs to be able to supply that load and more, about 30% more. If the inverter cant supply the load, it will shut down and you could be left in the dark until its reset.
Inverters have a continuous rating and a surge rating. The continuous rating is the maximum the inverter can supply without overheating and shutting down. The surge rating, usually many times the continuous rating, is the maximum the inverter can supply for a few seconds ( or minutes, depending on model ). Most loads, especially large motors, draw more power at startup than normal running, so we need this extra surge capacity.
Inverters also have a battery voltage rating. 12, 24 or 48 is common, the higher the better. A higher battery voltage means you can use thinner wire to carry the same power, and as a rule efficiency is better. The simple rule with inverters is buy quality and the highest rating you can afford.




Storage. Batteries. We need batteries to supply our energy when our power source cant, like solar panels at night time. Sizing batteries needs to take into account how far we can discharge them before we risk damage, usually to around 70% of capacity is OK. That is, we can discharge 30% of its rated capacity, we leave 70% unused, the less we discharge the better for the long life of the battery. Its also important that we recharge the battery as soon as possible, next day is ideal, but within a few days is a must. We also need to allow for battery efficiency, around 85%. Next, using a little maths...

	House Wh per day * Days
Battery Capacity (Ah) =	--------------------------------------------------------
	Batt Efficiency * Depth of Discharge * Battery Voltage

	10,000 * 1
Battery Capacity (Ah) =	-------------------------------------------------	= 816Ah
	0.85 * 0.3 * 48

So we need a 48 volt battery bank rated at 816Ah. This is assuming you have no power coming in from your solar panels for 24 hours, or you used all your power at night and nothing during the day. If we needed the system to run for 48 hours without any usable sunlight, the capacity would need to be 1632Ah.


There is no such thing as a 48volt 816Ah battery, so we need to build one with smaller batteries. A common deep cycle battery used in off grid systems is a Trojan T105, a 6 volt 225Ah battery. 8 of these in series will give us a 48volt 225Ah battery, multiply by 4 ( 32 batteries ) for a 48volt 900Ah battery bank.


It's worth noting battery ratings vary for manufacturer and duty, and are usually rated over a 100 hour discharge period, but to be really accurate we should use the figures for a 20 hour discharge, these will be less than the 100 hour rating. The battery datasheet should have these figures. As an example, the Trojan T105 in our example has a 100 hour rate of 250Ah, and a 20 hour rate of 225Ah.


These days there are alternatives to lead acid, like Lithium. Lithium batteries are much more expensive than lead acid, but do offer some advantages, like less maintenance, and a better discharge capacity of 70% instead of lead acids 30%. If we used Lithium batteries instead of lead acid for our system, we would only need a 350Ah battery bank instead of 816Ah. Worth considering.


In review, for a 10kWh system, remembering 10kWh is comfortable living that many of us are used to, you would need at least 2.4kW of solar, a 4kW inverter and 900Ah of lead acid batteries ( less for lithium ). But this is only a guide for a 10kWh system in ideal conditions, you should where possible increase the solar panel and battery capacity as money allows.


You can bend the rules a little. In my own situation, I have limited funds initially, so have to cut a few corners. I bought the best inverter I could afford, a 7kW ( 20kW surge ) 48v Latronics, as I need to run a welder and other workshop tools. I have 12 175Watt panels to give me 2.1kW of solar, and, at this stage, will be using 8 225Ah batteries to give me a 48v 225Ah battery bank.


 Yes my battery bank is too small, but I'll use it intelligently until I can afford to upgrade it. Jobs like washing the cloths, vacuuming the house, using the workshop tools will be done during the day while the sun is shining. Night time will be just lights, microwave cooking and TV, so I should have the capacity to get through the first few months until I can upgrade. I also have the option of wind power, there is a constant usable breeze at night and I expect I could harness 1kWh to 2kWh most evenings. And of course I have a generator if the battery state gets too low.




------------------------------------------------------------

What's the difference between Watts and Watt hours?

 
Sometimes there is a bit of confusion between the terms Watts and Watt hours. Fact is, Watts and Watt hours are very different beasts.
A Watt is a measure of Power. A Watt hour is a measure of Energy.
A Watt can be used to measure power in many different forms, for example we use Watts to measure electrical power, and we use also use Watts to measure mechanical power ( you car engine's power is can be measured in kiloWatts ( 1000 Watts ). To keep it simple, we'll stick with electrical power for this article.
We can work out watts using this simple formula.

Where : W = Watts V = Volts I = Amps

Watts = Volts X Amps Volts = Watts / Amps Amps = Watts / Volts

If we have a 21 Watt automotive light bulb, like a typical brake light, and we know it runs on 12V, then using the formula above we can work out it will draw 1.75 amps. The Watts is how much power the bulb is using.
A automotive spot light might be rated at 100 watts, so at 12 volts, it will draw 8.3 amps.
We can also use Volts and Amps to work out how many watts is used in a circuit. If we feed a heater circuit, like a bread toaster, with 240 volts, and its drawing 4 amps, then we can work out its drawing 960 watts.
So what's a Watt hour?
Watt hours is a measure of Energy. Energy is Power by Time.


A 100 Watt light bulb can use 100 Watts for 1 second, 1 hour, 1 decade. Its still a 100 Watt light bulb, but we need more energy to power the bulb for 1 hour than we need for 1 second, and a lot more for 1 decade. We call this measure of power over time a Watt hour ( Wh ).


If I power my 100 Watt light bulb for 1 hour, its easy to work out, we used 100 Wh's of energy. Watt hours = Watts by hours


If I power my 100 watt light bulb for 30 minutes, then we used 50 Wh's of energy ( 100W X 0.5h = 50Wh ). We used half as much energy as we needed to power the same bulb for one hour. If I power the same bulb to 2 hours, then we used 200Wh.


This is why our electricity bills measured in Watt hours, its a true measure of how much energy we used. Sometimes a house is using very little power, other times its using much more. The Watt hour is a measure of the total energy used.


We can also use Wh to measure the energy going into a battery from a power source, like a solar panel or wind turbine. If I have a 50 watt solar panel, and it was exposed to full sun for 5 hours, then it made 250Wh.
Now the fun bit. We can take the power out at a different rate than we put it in. If my 50 watt solar panel produced 50 watts for 5 hours, 250Wh, and this power was stored in a battery, we can take the same energy back out of the battery at a different rate. If I connect up a 100 watt light bulb, it will drain that 250Wh in 2.5 hours. If we used a 5 watt light bulb, it would last 50 hours. The same energy is used in every case.


In reality, its not a perfect world and there are losses every time energy is transformed from one type to another ( solar to electricity to chemical to electricity to heat and light ), so we will ALWAYS get less out than we put in.
You may hear the wind turbine builders comment that its better to build a turbine that can use low winds than high winds. A wind turbine that makes 100 watts for 10 hours will give you twice the energy as a turbine that makes 500 watts for one hour. In reality, the maximum power a wind turbine can make means very little when it comes to the energy it can supply. And as most wind is slow wind, you are better building a turbine that can make the most power in low winds, even if it means it cant make a lot of power in high winds.


Its like a big V8 sports car and a small economical 4 cylinder hatch. The V8 can go faster, and has much more power, but if you give both the V8 and the 4 cylinder the same amount of petrol ( energy ), its the 4 cylinder that will go much further.
Further reading.... http://en.wikipedia.org/wiki/Watt
 

Δεν χρειάζονται ολα αυτά τα Abra-Katabra:μια ματιά στον λογαριασμό της ΔΕΗ φτάνει!
Αμα διαιρέσεις τις κιλοβατώρες με το χρόνο εχεις μια καλή εκτημηση για την ισχύ που καταναλώνεις !

Καλημερα,
Μετα απο καιρο γραφω αλλα δεν πειραζει...
Κανω διαφορα αυτον τον καιρο και θα το ανακοινωσω οταν ολα τελειωσουν...

Οταν θελεις να πας σε λυση απε αυτονομου σπιτιου ενοητε οτι κανεις καποιες υποχωρισεις στην καταναλωση...

Ας πουμε δεν ξοδευεις οσο οταν εισαι στο δικτυο για οικονομια ενεργειας και υποτιθετε οικολογικη συνηδηση..
Ακομα ακομα βαζεις φουρνο με ξυλα,μαγκαλια,κουζινες και ψυγεια υγραεριου ηλιακους φωτισμους οικονομικους εναλακτικους τροπους θερμανσης και αλλα.

Οποτε δεν πας συμφωνα με το τιμολογιο αλλα συμφωνα με τους υπολογισμους της νεας σου οικολογικης ζωης....