Efficient Solar Energy Utilization

[HB13DISH]

Here is a 10 liters plastic container. It has a tap at the bottom which should make life easier to take water out or to cascade several similar containers. The only trouble is that hot water is usually at the top. But never mind, the water inside the container should reach the same temperature after several hours in the sun, and this shouldn't be a problem.

 

[Rick]

Just an idea for heating water in a sunny country.
Supposing you have a container of a size which is normally used for solar water heating systems ~120 liters, sitting on the roof top.
The container is totally transparent and for the sake of argument let us say it is made of glass (change it later for a less breakable material).
How long would it take for the water inside to get to a reasonable shower temperature of 40-50 degrees C?
After it gets to this temperature, cover it with an insulating material so that the temperature remains high for as longer time as possible.
I could try this with an empty plastic mineral water, which is reasonably transparent.
A bank of 60 empty bottles of 2.0 liters would get you 120 liters and would cost you nothing. At least save on the environment as you will be using them instead of throwing them.
A normal shower per person can be a lot less than this, but let us say this is for a couple with one child.

The problem you would get is bacteria growth if storing the water at this temperature. Most notable leigonella. I don't know about water regulations in your part of the world but in the UK they are very specific about this. Regardless of your water regs the danger will be the same.

 

[Turok]

Hello!
since i was in isreal,around 10 years ago,i receive newspapers every 2 month from this country,the write about the regulation,that the water is very low know,and the dead sea will dry out in around 30 years from now on,many countrys here,in europe,make plans,to bring,and sell there water to israel!
the also write in the articel about the regulations,of water,that is only allowed to wash the car,after sunset not before on day time,same,for the plans in the garden,to save water,same in australia in some region,the adice the people,to take shower together,to save water,

when you live in a house with 25 other seperate live rooms like you told,then it would be the best,that all together,bought a solarcell ,system,then it is cheaper for everyone!

my sister living also in house with 4 diffrent other familys separatly,and the cheapest way,is to find some one that can install you the panels,then you save alot of money,i dont know,how big your house is,and how much power you need in one year?
depents on that you have to spend more or not so much money in the cells,in my systers house we installed the cells by ourself,it coasts 1300€ shared coasts vor everyone the same price,now it is enough,to heat up the water by the sun,without electricity!
environmentally friendly gerneration of engergy
will be here more supported by the goverment!
again ,.you must know how much power you realy need over the year,then the installers when you need or have one,can tell you what kind of solar cell you need,others wise you spend to much money for!
here the use big cells,with big akku types that store the engery,from daylight,this you dont need in a sunny country
all the best in your planing,keep us informed!

 

[HB13DISH]

The problem you would get is bacteria growth if storing the water at this temperature. Most notable leigonella. I don't know about water regulations in your part of the world but in the UK they are very specific about this. Regardless of your water regs the danger will be the same.

I don't understand what you are saying Rick.
If I fill a 10 liters closed container like the one depicted with fresh water from the tap, leave it in the sun for few hours until the temperature reaches 40-50 degrees C, would it get bacteria growth?
How does this compares with a solar water heating system which has a tank of 120 liters on the roof top getting to 60-70 degrees C?
Would the bacteria not grow inside it as well?
This is the system that is being used for over 50 years now !!!!

 

[Lazarus]

If I recall correctly, it is advised that any hot water storage is maintained in excess of 55C for just the reason outlined by Rick.

I think it may vary depending upon the Regs applicable in different Countries because there is the counterbalancing issue of scalding to consider. Compromise.

In fact, in some hot countries, it is mooted that the "cold" water suply is potentially more prone to legionella infection.

 

[Turok]

hm,mabe he mean,when the plastic contrainer is old,then could be bacteria inside,when it always cleaned,or you use hot water,then the bactiria die also very quickly,

but when it closed,no insect coming inside,normaly nothing should happen then!

 

[Huevos]

deleted ...

 

[Rick]

There is bacteria in the water that comes from the water main. There is not enough bacteria to cause any harm though.

The regs in the UK state that hot water has to be stored above 55 degrees centigrade as most bacteria including leigonella starts to die. Cold water must be stored below 20 degrees as the bacteria cannont grow below this temperature.

If you fill a container with water and seal it, and leave it to warm up to say 40 degrees the trace amounts of bacteria in the water will begin to multiply. The only way to avoid this is to boil the water before storage in a sterile container to neutralise the bacteria in the water.

At 60 - 70 degrees in your roof top heaters the bacteria will die not grow so you are safe.

Generally the solar heaters in the UK will heat the water in secondary tank to around 18 degrees, this is then fed into the main hotwater cylinder which will be heated by a boiler to 60 degrees. The energy saving being that is takes less energy to heat water from 18 - 60, than it does from 4 - 60. 4 degrees being around the average temperature in the water main.

Hope that clears it up.

 

[Crisbe]

Thanks Crisbe. This is very interesting.
Can you please give me a link to the solar panel system that you considered and what was the maximum panel size?
Our building roof top without the solar water heating system can be large compared to your roof. Maybe 200 sq meters.
Perhaps we can have several solar panels, depending on the best places to fit them.
Apart from solar panels, is there any other solar possibility?

I looked at four systems from different suppliers. All were around the same price except for one type which had solar panels which fit in place of the roof tiles and look the same as a normal tiled roof. The average cost of an installation giving coverage of approximately 6mtrs x 4mtrs was about £13,000 UK pounds. This included the inverter system and wiring. (Also the cost of having an export meter installed by the electricty supply authority)

As we use between £700 to £800 of electricity each year you can see where I got the 15 year pay back time from. If I had opted for the best system, that looked just like a normal tiled roof it would have cost approximately £3000 more than the average "plant it on top of" system, so payback would have been even longer.

Having said all this, with a large flat roof area in a very sunny climate such as Isreal, I would have thought that the cosst of installation per Kw would be a lot less, because you would only be looking at one lot of wiring and it would be a lot easier to install, plus of course you would get a far greater output from the panels because of the stronger light levels and longer daylight hours at your location. I know we have several schools now in the UK that have solar panels on their flat roofs to cut down on their electricity bills, so the economies of scale must make it worthwhile. It should be the same on a large apartment block in a sunny place.

 

[HB13DISH]

Thanks Crisbe.
I take it that this size 6mtrs x 4mtrs is the one mentioned in your previous post which has a 2.5 KW maximum output.

Just trying to do the maths:
I haven't checked the cost of a similar installation in Israel, but let us assume it is the same here, then with a rate of exchange of 7 NIS/Pound, the cost for the whole building is
13000x7=91,000 NIS
As we have 15 apartments, then cost / apartment = 6066 NIS, which is a lot of money for anybody these days if paid in one lump, but might be OK if paid over a five year period (60 months) as each installment is ~ 100 NIS and each apartment gets back 60 NIS / month for "selling" electricity, which means each apartment pays only 40 NIS/month which is excellent. (see calculations below)
If we get on average 8 hours of daylight (sunshine)/day, we would have:
2.5 KW x 8 Hours = 20 KWH/Day
The current cost of KWH is 0.5 NIS, but we will get x3 this tarrif = 1.5 NIS per KWH > 20x1.5= 30 NIS/Day > 2 NIS/Day/Apartment
91,000 NIS Divided by 30 = 3033 Days > 8.3 Years to break even.
Either I made a mistake in my calculations or this size has higher output than 2.5KW.
At any rate, if this is correct, then it seems that this is certainly not such a good bargain, as people would expect a much shorter break even period, something like 2-3 years, otherwise they will not go for it.

If we get rid of all the solar water systems in order to have a much larger area to put more solar panels, then we would need to pay a lot more money for the installation cost.
Will wait for a much cheaper solution or better offers by the authorities.

 

[easysat]

Here's some figures pinched from a French environmental agency site.

The annual solar energy hitting your panels runs from less than 1220 kWh/m2 of panels in northern and eastern France (Lille and Strassbourg), 1220 to 1350 kWh in Western and central France (Brittany, Paris, etc.). If you're on the Mediterranean coast, you can expect 1620 to 1760 kWh rising to more than 1760 kWh/m2 on the Cote d'Azur (Nice). The conversion efficiency is somewhere in the region of 12-15% rising to 18% for mono-crystalline types. The panels should last 25 years or so. You also need a dc to ac convertor, which needs to be replace every 8 or 10 years, costing between 1000 and 2000€.

The cost of the panels themselves including installation in France is about 6000 to 7500 € (excl. tax) per kW. A 3kW installation corresponds roughly to 30m2 of panels. On top of this you need to pay another 800 to 1500 € for the metering equipment and connection to the public electricity supply network. In France the economics make it worth your while to sell all your solar power to the network rather than just the surplus.

I remember reading somewhere that solar water heating wasn't worth the cost in northern France. The argument ran along the lines of not getting much useful hot water during half the year , when you really need heating, because the air temperature is low. In summer the hot water will only be there in the evening and not when most people take their showers in the morning. However government grants for electric solar panels make them a reasonable investment (maybe with a return of 5% pa) even in the north because the panels will still work in weaker winter light and the fact that it is cold outside doesn't bother the photovoltaic process.

 

[Crisbe]

Sorry about the second post guys. I was at work during my lunch break today and looked at the posts, started typing away like mad and then got called away to a breakdown on a machine. I must have hit the send button without realising it and thought I hadn't sent it , as by the time I got back to my PC it had gone to sleep and the forum had logged me out. I thought as soon as I get a chance tonight I must send the answer again and flicked through the posts, completely missing the fact that my lunchtime effort had actually appeared on here. I know, I know, I am going mad in my old age, but I have had a hard day. (That's my excuse and I am sticking to it) You don't have to be mad to work where I do, but it helps!

 

[Turok]

Hello!
this is a very complex subject here,so i dont know all english words,that i want to tell,and translate it with google to subsribe the situatiohn here,hope it sounds correct

I will probably never buy solar panels, there are a total of too little sun
in the mauntains,in the winter the sunset is on 2 a.m daytime
in summer time on 19,30

Our community is now doing for each household digs for heating!
A central heating plant, where native timber is burned, and all households may connected out about special piping, in 2 years it is finished, you need not buy oil to heat or electricity for that is, all centrally heat that come over the pipes,you simple have on of power swtich on your heater thats all!

the power here is very cheap,water comes ´direkt from the mauntain,into the turbines,and at 10 am,in the night you got 30% dicount again for the night power!
our powercompany build a new power turbine systeme, for 400 million € and sells there power all over europe to all company!

but the heating system above,will be cheaper then the oil companys,and cheaper then the power ,we will see!
they call it clean engery from nature,that comes from the local wood!

here a picture of it!



_http://blog.fernwaermeforum.net/wp-content/uploads/2009/07/Fernk%C3%A4lte-KRaftwerk1-300x225.jpg

 

[Crisbe]

Just a thought. The way technology is advancing in terms of production of electronics in a few years time the cost of PV cell arrays might come down a lot. Especially if there is more demand and they step up production. Installation costs will always be cheaper if the systems are put in at the time of building and I think we will see more and more PV systems being built in to buildings as time goes by. After all, sooner or later the oil and gas will run out and all that will be left are renewables and nuclear.

 

[Turok]

Hi!
a couple,of month ago on the german channel zdf was a report,that is posible to convert some heater systems,from a company,that specialeized in this,and after that,you can heat with popkorn,lot cheaper then oil and power!
but back to the solar engery,what companys exitis that make the panels,and who have the best quality of the value of money you can get?
i dont know any brands yet,but maybe there also some bad procucts on the market,that looks good,but not collect so much power then others ,in the same size and price range!
this is real very diffucult to find out,before you buy a cell,what is good and what not!