New smart timer from CBI

[ians]

So there are pros ...but unfortunately like everything ... there are cons.

One of the cons is the lack of control over the temperature of the geyser ... as I am experiencing first hand.

I have had the ASC unit installed at home for almost a month ... has it saved me money ... yes ( total consumption for Novemer 125 kwh X @R2.09 =R261.25) ... but at what cost ... today the unit has been bypasses until I can find a better solution ... the consumption has already passed the 6 kwh average daily useage and it is only 12 midday.

The family have had enough of cold and luke warm water baths.

There are a few solutions to this issue ... I can fit a bigger element to reduce the time to heat the water ... turn up the temperature on the thermostat ... fit a device with built in temperature monitoring/control.

The question I keep asking myself everytime I fit a timer or device to a geyser ... do you actually save money?

Unless you mount the geyser next to the tap and fit a geyser with a big enough element to heat up in a short time frame ... you gonna have losses be it via the cold water in the pipes ... when the geyser mixes the cold into the hot as it fills.

The good ol donkey outside with an open fire ... could be the cheapest solution.

[GCE]

Hi
I was involved in testing the efficiency of a new geyser that was being designed.
There were all sorts of tests run and some basically the same as fitting a timer to a geyser.

I was asked the question often about fitting timers to geysers and ended up fitting a KWH meter and timer to my own geyser - One week I run using the timer and took note of the units used and the next week without timer taken note of units used .
I did this for about 6 weeks to average things out.

At the end there was no real difference whether you had a timer or didn't and it actually seemed to use more energy when a timer was in play.

In the end the energy used is directly proportional to the amount of water used and is determined by the formula
q=cmΔT
where
q - amount of energy used
cm - heat capacity of water
ΔT - change in temperature

if you use 10 liters of water you will need to heat the 10 liters .When you heat it makes no difference unless you are on a time of use tariff and the units cost less in the middle of the night then during the day or during peak times.

The only way to save electricity on a geyser is , use less water , or reduce the temperature .

[Justloadit]

Another solution is what I have designed - Use PV panels to heat your water.
I installed my latest design for a dual geyser system. That is 2 off 150 litres with 10 off 260W PV panels.
The installation was completed on Tuesday last week.
This has been a week of overcast weather, and clocked just over 10kWH on Wednesday last week, which was a little cloud day, and bearing in mind that the geysers were starting from a low temperature of 34° C each due to being switched off during the whole installation process. By 17H00 both geysers were at 60°C when the thermostats shut off.
Every day the water temperature has been at 60°C when the thermostats have disconnected the elements
Went to check the reading today - Saturday after sunset, and the accumulated energy used from the sun is 48.891kWH, making it an average of 9.778kWH per day. I pay an average of about R2.80kWH, it is high because what is not informed to users, here in Johannesburg, I pay over and above the electricity usage because I have a post paid meter
Network Surcharge of R 19.68 excluding VAT
Service Charge R147.74 excluding VAT
Network Charge R 596.18 excluding VAT
Every day since then has been and average of 6 to 7kWH

So since I installed the system, I have already saved R 137.00 or R 27.42 a day.

If any one is interested, got www.usedasun.com or send me a private message and I will send you the information for the Usedasun Solar geyser system

[Dave A]

if you use 10 liters of water you will need to heat the 10 liters .When you heat it makes no difference unless you are on a time of use tariff and the units cost less in the middle of the night then during the day or during peak times.

The only way to save electricity on a geyser is , use less water , or reduce the temperature .

You're sort of right, particularly if your geyser has great insulation. However, a trial I did a Geyserwise timer system on my gravity geyser a few years ago yielded some pretty good results. It isn't a particularly well insulated geyser

I was going to try their pv dual element system, but the ELU problem has put that thought on hold.

Might have to give Justloadit's usedasun system a go...

For all the benefit of energy saving (or not), what I really love about the Geyserwise setup is the easy control it gives you on water temperature settings.

[GCE]

Hi Dave

On a gravity feed geyser you will see good results as the efficiency is so bad - On the older pressure geyser there could be a slight saving , but debatable , on the newer flange mount elements you don't see it due to the element design and water flow around the element .I was given a story around the design of the element , thought it was BS but on trying different things it does seem to be more efficient. The insulation material has also improved dramatically
I like the geyser wise system due to the ease of adjusting temperature which to me is were the savings come from as it is more accurate then the bimetal strip.

With regards to the PV dedicate to a geyser in my mind makes no sense at the coast. I understand the logic in near freezing temperatures where the convention solar water type systems burst seals etc.
At the coast PV panels ability to absorb energy sits at around 30% max whereas solar water type system ability is around 70% .

To me I would rather take the money spend on panels dedicated to a geyser only and use them for panels to " gridtie " within my own network so that if the geyser is at temp I can use the excess energy to reduce my account on other items.
I only have 2KW of PV at the office along with a Tesla powerwall and run for days without using any municipal power, but then I am a stingy bastard that does not allow an aircon in the office.

[ians]

My geyser is an old gravity geyser ... avg consuption using the timer which included cold showers and baths ... 6 kwhr
with the ASC unit on bypass ... avg consumption ... 8 kwhr per day hot showers and hot baths ... no geyser blanket installed.

I have a 1 kw element in my geyser ...set to 55 degrees.

For R125 extra per month ... for hot shower and a happy wife ... worth every cent.

[Justloadit]

Hi Dave
At the coast PV panels ability to absorb energy sits at around 30% max whereas solar water type system ability is around 70% .

Can you show any documentation attesting to this?

Whilst the coast gets less sun radiance than inland according to the studies, except when you are lying on the beach , the scientific study shows that Durban gets approximately 2/3 less than Johannesburg per annum.
I have been reading when there is no cloud cover at midday approximately 2.6kW out of my 2.6kW array, which translates to over 1000w per square meter of sun radiance. The 1000w/m square is the reference that PV manufacturers use as a reference that their panels can produce electricity at 25°C, so my panels are producing the 2.6kW at a temperature around 50°C indicating a higher watts per square meter.

Solar Radiance Maps

[GCE]

With regards to the PV dedicate to a geyser in my mind makes no sense at the coast. I understand the logic in near freezing temperatures where the convention solar water type systems burst seals etc.
At the coast PV panels ability to absorb energy sits at around 30% max whereas solar water type system ability is around 70% .

.

My statement was a bit jumbled and confusing even to myself now having read in again.

At the coast the temperatures are moderate and we don't get close to freezing vs further inland.

At the coast using a solar water heater , the chance of the pipes freezing during winter are almost zero vs some inland areas where the temperatures will drop below freezing at night and could cause the water to freeze in the pipes exposed .Once the water freezes it tends to expand and burst seals , joints etc.
The maintenance on a solar water heater system in colder areas would increase the costs of the system over the longer term and so in my mind would be more cost effective in the long run to use PV panels to produce energy through an element to heat the water.
At the coast the scenario is different.

The efficiency of PV vs water solar heater - The efficiency of PV extracting energy from the sun is at around 30% per square meter vs Solar water heating at around 70% per square meter .
I cannot find the notes from a course I did with Solar Edge inverters which showed the tests and graphs of both technologies to back up the statement.
I did find the following piece in-between notes that I have pasted below.

Matuska, Tomas & Sourek, Borivoj. (2017). Performance Analysis of Photovoltaic Water Heating System. International Journal of Photoenergy. 2017. 1-10. 10.1155/2017/7540250. Performance of solar photovoltaic water heating systems with direct coupling of PV array to DC resistive heating elements has been studied and compared with solar photothermal systems. An analysis of optimum fixed load resistance for different climate conditions has been performed for simple PV heating systems. The optimum value of the fixed load resistance depends on the climate, especially on annual solar irradiation level. Use of maximum power point tracking compared to fixed optimized load resistance increases the annual yield by 20 to 35%. While total annual efficiency of the PV water heating systems in Europe ranges from 10% for PV systems without MPP tracking up to 15% for system with advanced MPP trackers, the efficiency of solar photothermal system for identical hot water load and climate conditions is more than 3 times higher.

[Justloadit]

Hi GCE

The reference from Matsuka is in relation to the type of conversion process one uses when using PV. There is the MPPT tracking which gives the most efficient conversion for PV panels. I do not want to go further than this in explanations, as there are many good quality videos on Google explaining the type of conversion process available.

The crux of the mater is the word "Efficiency", in relation to the discussion at hand, efficiency does not play into the process of heating water, but the efficiency related here is the amount of energy one can extract from one square meter of surface area. If you have an empty roof, and you need 3 square meters or one square meter to get the water heated, does it really even matter?

Right now lets look at evacuated tubes versus PV panels.

Evacuated tubes work, but the efficiencies thrown about by installers are very optimistic. Bear in mind that I have had an evacuated 12 tube system on my roof for 10 years, so I am very in tune to what it can and can not do.
Some points that come up with measurements that I did as follows : -

Evacuated tubes
Summer
Starting temperature most mornings at 6AM was approximately 45 degrees, because my geyser timer would switch the geyser on from 5 to 6 so that I could have a decent shower in the morning.
End of the day at 17H00 maximum temperature of my geyser 52°C - no one at home to use the hot water. After the wife had a shower, temperature dropped to 42°C, there was sufficient water for my shower. Being summer, water does not have to be very warm. Temperature loss over night approximately 5°C so at 05H00 the geyser temperature was usually between 35 and 37°C.

Winter
Starting temperature most mornings at 6AM was approximately 43 degrees, because my geyser timer would switch the geyser on from 5 to 6 so that I could have a decent shower in the morning.
End of the day at 17H00 maximum temperature of my geyser 47°C - no one at home to use the hot water. After the wife had a shower, temperature dropped to between 32 and 37°C depending on how long the shower took. There was insufficient water for my shower, so switch the geyser onto mains. Usually took 45 minutes to bring the temperature above 45°C for my shower.

Replacement PV panels, I only have summer measurements for now, but one can extrapolate to winter because of studies done on existing installations that we have done
Set both geysers thermostat to maximum point which is approximately 65°C

Summer - I have 2 geysers running on 10 panels of 260W HV PVs -
Starting temperature most mornings at 6AM above 50°C on my Kitchen geyser, and above 42°C in the bathroom geyser as referred to above. Depending on the day, a clear day, by 12H00 both geysers at 65°C, an overcast day, between 13H00 and 14H00 both geysers over 65°C
After the wife had a shower, temperature dropped to 52°C, there was sufficient water for my shower. Being summer, water does not have to be very warm. Temperature loss over night approximately 5°C so at 05H00 the geyser temperature was usually between 45 and 47°C. Still hot for the morning shower, and the kitchen geyser around 50°C, depends on the number of pots get washed the night before.
Since installing it, I have not switched mains on yet. I read between 6.5 to 7.5kWH per day for both geysers running of PV

Winter, extrapolating from studies on other geysers installed, in the highveld we do not usually get overcast days in winter, so I reckon that by 14H00 hours, both geysers will be at 65°C.
Not sure of the exact losses over night, and the water replenished during hot water usage. Will have to wait for winter to get exact numbers. Experience from other installations done, the performance was good.

The issue with evacuated tubes is that there is a major issue between the balancing of the number of tubes for summer and winter. Winter is the time that the hot water is the issue not summer. In winter we want a higher water temperature, both to deal with the cool air in the bath room which appears to be colder when bathing, and also to deal with the heat loss differential in the ambient environment due to the winter cold.

Most evacuated tube systems are designed for summer, so that the water temperature does not go too high, as there is no way of controlling this save for reducing the amount of heat capturing, if there are too many tubes, then the water boils which can be an issue for geyser cylinders which must not only handle the temperature, but also the higher pressure.

Now with the 40% reduction in sun radiance in winter, the number of tubes that is selected for summer, just does not heat the water sufficiently in winter with out a mains back up. So the system does not quite cut it.

Placing more tubes for the winter usage then requires more controls which increases the over all cost of the evacuated tubes. This is usually not explained to customers, and customers think they are helpig the planet with out realizing that they are subsidizing the extra water heating with mains.

[GCE]

Hi
He ,Matsuka, also makes a statement with regards to solar water heating

While total annual efficiency of the PV water heating systems in Europe ranges from 10% for PV systems without MPP tracking up to 15% for system with advanced MPP trackers, the efficiency of solar photothermal system for identical hot water load and climate conditions is more than 3 times higher

There are numerous articles on advantages and disadvantages of each system .

A lot depends on what is being sold as to which articles are high lighted.

I am selling neither