Yield Production Hot Water Electric

[PVresistif]

Electric Hot Water Production: yield and costs

The notion of thermal efficiency is an important notion that is important to understand in order to be able to decide the design of an energy installation such as hot water production.
In general, the output is defined as the ratio of the useful energy Eu, to the total energy (or paid) And; the difference is the losses Ep, so Et = Eu + Ep

R = Eu / Et = Eu / (Eu + Ep) where R% = 100 / (1 + Ep / Eu) occurs

In this way, it is clear that for a good return it will be necessary to have the smallest loss / useful energy ratio (Ep / Eu); For fixed Eu, this will be achieved by minimizing losses Ep and minimizing losses it is also a way to reduce total consumption and total cost of energy consumed.
In view of this formula, to reduce our consumption of resources - both natural and financial - it is therefore necessary a good return- by a thoughtful design during the investment to increase R and reduce Ep -and by an eco-responsible way of life to reduce Eu consumption.
For a production of hot water by electric water heater, Eu will be the energy needed for the hot water used and the losses Ep will be the losses due to the walls, the losses due to the pipes which also lose energy, but also the losses due to the water contained in the pipes that it is necessary to send to the sewer before actual arrival of the hot water at good temperature. These losses of energy and water can quickly become very important in case of great distance between the water heater and the points of drawing.

An important notion also in thermal, is to understand that like the water that flows from the top to the bottom, the energy also is exchanged - or flows from the top (high temperature) downwards (low temperature). This law is unavoidable and this has the consequence that any difference in temperature implies an exchange of energy or otherwise says an unavoidable loss that implies a financial loss associated.
Thus it will be impossible to maintain a system energetically stable or appears a difference in temperature; and therefore, to maintain stability, it will be necessary to compensate for these losses by an equivalent supply of energy which will have to be paid and which thus deteriorates the efficiency of the system.

For example, if you take a domestic water heater from 200 L, it is in contact with the environment in which it is placed, and therefore heat exchange by temperature difference. If the thermostat is set to 65 ° C and that the water heater is in the bathroom heated to 20 ° C, there is a permanent exchange - a constant loss of energy - proportional to the difference of temperature is 45 ° C and the surface of exchange (either the outer surface of the water heater, or about 2.1 m2 for an 200 L appliance). This constant loss will be offset by the start of the resistance to maintain the water at 65 ° C.
For a water heater of 200 L the losses are given by the manufacturers by 24 and are of the order of 1800 Wh per day or 75 W per hour (see appendix a, manufacturer data for deviation 45 ° C); it is a strong light bulb constantly on 365 days a year or 8760 h / year; the losses will be 75W x 8760h = 657000 Wh = 657 kWh.
Knowing that 1 kWh costs 0.15 €, for a year it is 98.5 €, it is not negligible anyway; on the other hand, if this water heater is in your garage at an average temperature of 10 ° C, the temperature difference is 55 ° C instead of 45, and the annual losses will be increased by either 657 * 55 / 45 = 803 kWh or 121 € lost per year.
If this water heater is outside or in a cold room - such as a thermodynamic water heater - the losses are even more important.
From this it follows clearly that in order to reduce the losses it is necessary at the same time to reduce the losses by the walls and the losses due to the length of the pipes: from where to install the water heater in a warm room and close to the points of drawing; ideally it will be installed in the heated volume and closer to the bathroom and kitchen.
Of course we can - and we must - consider that in the case of the water heater in the heated volume, losses are zero because recovered during the heating season at least during the heating season is 240 days per year or so; in the case the losses are reduced and become 657 x (365-240) / 365 = 225 kWh or 33 € / year; on the other hand if it is installed in your garage, the whole thing is lost and it is therefore 803 kWh is nearly 4 times more annual losses and thus 4 times more money thrown by the windows!
By installing your water heater in the bathroom, for example, this solution minimizes energy loss, water loss and investment (standard water heaters, shorter pipes and no insulation). invest the minimum and you pay the minimum to produce your hot water is the best solution for you alone; so do not wait for no standard or energy professional association to suggest such a simple and efficient design, their interests are not yours.
Notes:
- you can verify that a water heater always has a better performance and a minimum cost for the case where it is installed in the heated volume because the losses are recovered during the heating season (about 75% of the time) and the Water losses are reduced because the length of the pipes is reduced.
- For an individual thermodynamic water heater (CETI), the efficiency is much lower, because the losses are greater (losses per area greater because cooler atmosphere, significant water loss because distant device due to noise) while the energy consumed Eu is much lower; despite this, the total cost is higher for a production lower than 180 L / day (see appendix c for the selected hypotheses), which is a shame given the additional investment; in any case, check the return time - number of years to recover the additional investment - before embarking on this complex solution and subject to maintenance; do not forget especially to take into account the cooling of the room where it is with the possible impact on the note of heating of the adjacent heated premises for a CETI on indoor air.
- In all cases it is necessary to look for the lowest cost which will be obtained most easily by a water heater in the volume heated close to the appliances served; moreover, an electric appliance ages much better in a heated room than in a cold and humid room (on the other hand you must respect the minimum distances to the walls of the shower or the bath).
- The thermodynamic devices will be of interest only in the case of a significant consumption throughout the year. (see performance graph in consumption function)
- The capacity of the water heater will also depend on the tariff used; in the case of a night rate - however, beware of its possible surcharge - it must have a higher capacity but in case of base rate, use rather a small capacity (which will minimize losses) of lower power with a water heater that will be used Longer.

NRemember: When you decide on the location of your water heater, you will very heavily impact the performance of your hot water system throughout its lifetime with heavy financial consequences every year.

For those who are interested in the small spreadsheet excel me a message on the site; it will allow you to check your own installation I hope, or rather to convince you to perform a most efficient installation.
References :
- Data sheet thermodynamic water heater (feb 13) http://www.ademe.fr/chauffe-eau-thermod ... duels-ceti
Annexes:
- Annex a: manufacturer data (losses by the walls)
- Appendix b: Sample Performance Worksheet
- Appendix c: graph worksheet based on production

[yves35]

Electric Hot Water Production: yield and costs


For example, if you take a domestic water heater from 200 L, it is in contact with the environment in which it is placed, and therefore heat exchange by temperature difference. If the thermostat is set to 65 ° C and that the water heater is in the bathroom heated to 20 ° C, there is a permanent exchange - a constant loss of energy - proportional to the difference of temperature is 45 ° C and the surface of exchange (either the outer surface of the water heater, or about 2.1 m2 for an 200 L appliance). This constant loss will be offset by the start of the resistance to maintain the water at 65 ° C.
For a water heater of 200 L the losses are given by the manufacturers by 24 and are of the order of 1800 Wh per day or 75 W per hour (see appendix a, manufacturer data for deviation 45 ° C); it is a strong light bulb constantly on 365 days a year or 8760 h / year; the losses will be 75W x 8760h = 657000 Wh = 657 kWh.
Knowing that 1 kWh costs 0.15 €, for a year it is 98.5 €, it is not negligible anyway; on the other hand, if this water heater is in your garage at an average temperature of 10 ° C, the temperature difference is 55 ° C instead of 45, and the annual losses will be increased by either 657 * 55 / 45 = 803 kWh or 121 € lost per year.
If this water heater is outside or in a cold room - such as a thermodynamic water heater - the losses are even more important.
From this it follows clearly that in order to reduce the losses it is necessary at the same time to reduce the losses by the walls and the losses due to the length of the pipes: from where to install the water heater in a warm room and close to the points of drawing; ideally it will be installed in the heated volume and closer to the bathroom and kitchen.
Of course we can - and we must - consider that in the case of the water heater in the heated volume, losses are zero because recovered during the heating season at least during the heating season is 240 days per year or so; in the case the losses are reduced and become 657 x (365-240) / 365 = 225 kWh or 33 € / year; on the other hand if it is installed in your garage, the whole thing is lost and it is therefore 803 kWh is nearly 4 times more annual losses and thus 4 times more money thrown by the windows!
By installing your water heater in the bathroom, for example, this solution minimizes energy loss, water loss and investment (standard water heaters, shorter pipes and no insulation). invest the minimum and you pay the minimum to produce your hot water is the best solution for you alone; so do not wait for no standard or energy professional association to suggest such a simple and efficient design, their interests are not yours.

the first thing to do, which at a very quick return: (qq months), is to offer your balloon a jacket in glass wool or other.On had caused for example there:
http://forums.futura-sciences.com/habit ... mulus.html

The fact of placing the balloon in the heated volume is discussed: the losses contribute to heating in winter but also in summer. But here too, to be better, improves things.

yves

[torrent sites]

I've been thinking about "putting a coat" on my water heater (300L in my cellar) for a while.
Any time I wonder if isolating the water heater is not likely to create condensation on the outer wall and in case, eventually, the corroded

[izentrop]

I've been thinking about "putting a coat" on my water heater (300L in my cellar) for a while.
Any time I wonder if isolating the water heater is not likely to create condensation on the outer wall and in case, eventually, the corroded

Hello,
Condensation appears on cold walls, so no reason http://www.apper-solaire.org/Pages/Fich ... /index.pdf

[torrent sites]

Ok, that reassures me.

I'm going to do a little 100 glass wool insulation session (I still have some roofs left)

[chatelot16]

improving the insulation of an electric water heater is easy with a very old water heater that has a simple thermostat that only measures the temperature of the water ... but with the current standard thermostat is no longer possible! additional insulation makes the temperature of the thermostat go down and it hangs as if it were broken down: it happens in summer when we put too much glass wool around the water heater

it is therefore essential to make the thermostat to increase the insulation ... because the current thermostat is bad

[Forhorse]

The cumulus thermostat must be the same since 50 years ...

[izentrop]

I do not see why an electronic thermostat would be more problematic.
A mechanical thermostat includes a probe placed in the conduit of the galvanic anti-corrosion anode and the other part under the resistor. In the electronic case, the probe is probably a thermistor. http://www.chauffe-eau-pieces.fr/sondes ... 00446.html

The precaution to take in 2 cases is not to cover the electrical / electronic part (protected by a hood under the water heater) to keep it at room temperature.

[chatelot16]

what I call modern thermostat is already quite old: it is fully mechanical, it contains 2 thermostat: the main thermostat has adjustable temperature, and a backup thermostat that measures the temperature of the box, and cut if there is a bad contact that overheats and cuts permanently until it is rearmed by a button

with this kind of thermostat it cuts off if you isolate the water heater: I saw it for a water heater in an attic, with some turns of glass wool: the only solution was to remove a little insulation in down to cool the thermostat

this is another reason to make an electronic thermostat separate from the water heater ... it will not only avoid this problem that prohibits good isolation, and it will also allow to have a double set of temperature, in the kind 60 ° on edf and 95 ° when there is solar electricity

[izentrop]

No wonder in an attic where the room temperature can go up to 50 ° and more. Even without over-insulation, there is a risk of disjunction if it is poorly ventilated.
The safety thermostat, whether standard or thermistor does not change the fact that it is housed in an open conduit below.

Modern or solar water heaters can perform anti-legionellosis cycles and other functions such as delayed heating at night.
overheating safety is always ensured by a bulb thermostat. https://elyotherm.fr/thermostat-chauffe-eau-electrique