Query on smart meters

John_F

Hello all, said id reopen this to stay with topic

I am a farmer and we are currently looking to purchase a bulk milk tank. There are two methods of cooling milk.

1) direct expansion (DX) where evaporator plates are incorportated to the bottom of the tank in direct contact with the milk, liquid refrigerant expands inside the evaporator taking the heat out of the milk. This is the most efficient way of cooling milk in terms of kwhs consumed per litre of milk cooled, but must operate at day rate eletricity (as soon as milking is being done and milk entering tank).

2) Ice Bank (IB) cooling is where a seprate tank builds up ice water and then this ice water is sprayed onto the bottom of the tank to cool the milk, this combined with a plate cooler is the fastest way to cool milk (known also as instant cooling). This system is less efficient in terms of kwh consumed per litre of milk cooled. BUT the ice builder can build ice water at night rate electricity, making it a cheaper to run system

My q is about the smart meters and how they would affect a person to go with direct expansion (using day rate and peak rate) or to go with ice bank using night rate only

here are my sums: from using the table 1 here http://www.farmersjournal.ie/2005/0827/farmmanagement/dairy/feature.shtml

DX will cool 68 litres of milk in 1 kwh to 3 deg c. so this means 100 litres in 1.47 kwh or hours

IB will cool 45 litres of milk in 1 kwh to 3deg c. so this means 100 litres in 2.22 hours

we are with airtricity so at a day rate price of 13.92c/kwh means 20cent per 100 litres on DX. On an IB tank the night rate is 7.36c/kwh costing 16 cent per 100 litres, a saving of 4 cent per 100 litres cooled from ~37 deg c to 3 deg c (all figures exclude pre cooling of milk)

Now when i came across this slide show on smart metering http://www.cer.ie/GetAttachment.aspx?id=05178eb0-8911-49a3-91e3-56104aebd4c1 and on page 9 it gives a guidee to prices of day rate 14 cent, peak rate 20 cent and night rate 12 cent per kwh

using these figures, for a DX tank which would come on at milking time to cool the milk, cooling half in the morning and half in the evening, so lets say 50 litres will take .735 hours at day rate in the morning of 14c/kwh gives 10.29c per 50 litres. And half thee milk in the evening at peak rate is .735 hours to cool 50 litres at a peak rate of 20c/kwh is 14.7 cent per 50 litres, totalling 24.99 cent per 100 litres cooled in a day.

for an IB tank at the above links rate of night rate meeans 100 litrees in 2.22 hours at a rate of 12 cent per kwh is 26.64 cent per 100 litres in the day

are my calculations right in saying that even with smart metering the DX tank is cheaper to run

sorry for long post in advance

Ghost Estate

Macha wrote: »

Erm..here you get into techy territory that I'm not 100% familiar with.

What is intended is to set up a Home Area Network where each relevant appliance (ie demanding electricity (fridge/oven/dishwasher) or offering electricity (wind turbine/PV) would be integrated into the network, I assume using some sort of wireless technology. Then the data from these applicances can be fed into a CPU that will then optimise the demand and supply of electricity in whatever way the occupant wants it to be

it would more sense to send it over the power network itself. each individual device can decide whether or not it's too expensive to switch on. some fridges already delay switching on if the grid is having trouble (low frequency)

For example, you might want electricity from your PV to be used up first before you take energy off the grid or you might want to only turn on the washing machine when electricity costs go below a certain level, etc.

as would happen by default anyway if you had a grid tie inverter installed. no smart grid needed

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i'd be worried about the privacy implications of all of this too. garda, esb, the council and god knows who else knowing everything about what appliances you use and when

dowtcha

re milk cooling, unless you are on a three phase power supply, most single phase 220V meters are not smart meters and cannot record peak usage, only night/day usage. Also regarding your costs, it may be stating the obvious, but it is worth keeping a track on cooling times, as an indicator on plant performance/ service condition - as this will change your cost basis, just as fast as price changes on electricity supply. I should say on meters also, that getting a manually read meter changed to a smart meter is not readily available from ESB - they are on a trial basis only> The ESB want to see if the extra functionality of the meter is used by customers sufficiently to justify the extra expense