The Renewable Heat Incentive

[An Inspector Calls]

Rota cuts due to lack of generating capacity are clearly more likely in winter also as the peak load is in winter, in the UK.

We have not had widespread rota cuts since the industrial disputes of the 1970s, but it could happen again, and would be most likely in severe cold weather.
Not a good time to be reliant on electricity for heating.

We had one day of rota cuts more recently, in mild weather, due to a most unusuall series of generating plant breakdowns.
Report here
http://www.nationalgrid.com/NR/rdonlyre ... Issue1.pdf

Supply shortfall may occur at any time of the year - in summer a lot of plant will be withdrawn for maintenance (on a grid-planned basis). It's a VERY rare event as we all know. We don't want another "Emperor's Clothes" scare going the rounds. In fact, the planning to match predicted demand (which is accurate to 3% for the elctricity market - much better than the gas market) against generation is carried out on a continual half hourly basis, with longer views for maintenance planning. Generation and load are matched to achieve a less than 1 in 20 probability of generation shortfall (i.e. one event every 20 years). It's done by intersecting probability functions of load requirement (Gaussian) and generation (previously Gaussian but now increasingly complicated by wind (Weibull).

To try and build a case for the electricity grid being beset with major and repeated interruptions is a waste of time. I am aware of the remarks of Holliday, but frankly I think it's a great deal more likely that he'll be moved on after that performance, than rota cuts being commonplace.

If it were a commonplace event then I would expect emergency boiler power supplies to be commonplace - but I know of no manufacturer who makes one. Gravity feed will work, but only for part of the house with solid fuel.

The grid event you refer to was not a rota cut. It was a low frequency incident as is obvious from the title of the report:
"Report of the investigation into the automatic demand disconnection following multiple generation losses and the demand control response that occurred on the 27th May 2008"

The cause is well described therein:
"On the morning of 27th May an unrelated and near simultaneous loss of generation at Generator A (345MW at 11.34am) and Generator B (1237MW at 11.36am), totalling some 1582MW at the time of loss, gave rise to a drop in system frequency to 49.14Hz. Following this there was a further, as yet not fully explained loss, which led to a further drop in system frequency to 48.795Hz."

All very coy! Generator A was Longannet, B was Sizewell, and the "further, as yet not fully explained loss" was the wind fleet tripping because of low frequency.

There is one disturbing aspect of this for our friends in the south. If there are shortfalls in generation, the effect will be hardest felt in the SE of the country because most of the generation is in the north and west, and the SE will experience both low voltage incidents as well as low frequency. I've got my nice nuke down the road.

[An Inspector Calls]

All the more reason for a forum, so we can discuss your ridiculous assertion.

The trouble with heat pumps is that they are at their most efficient during the summer when they are not required and at their least efficient during the winter when they are. Yes, you can get a COP of 4 or maybe 5 from them but that is during the summer when you can get hot water from solar. During the winter you are more likely to get a COP of 2 or 3, unless you have a source of free heat to work from. The Hockerton Housing Association use the heat from their conservatories to increase the COP of their heat pumps but they are small ones heating their Domestic Hot Water supply.

Your CoP figures are odd.

My heat pump is the older flavour of Danfoss DHP series. The quoted CoP (brine at 5, outlet 35C) is 3.4. I didn't expect anything like that quoted figure because I'm not using underfloor heating. My energy averaged CoP over a year is 2.95, which means my energy price is 3.25p/kWh. In other words, I am achieving gas grid prices, or better, and I'm not connected to the gas grid. You don't get high CoPs in summer heating hot water because the target temperature is 50-55 C. But then, you don't thrash a lot of energy in that mode - water heating is only about 3.5 MWh/annum/house.

Another way of looking at this is that I have reduced my area weighted U value down from 0.54 (part old house, solid floors, solid walls) to 0.18 - near PassivHaus. I've done this for ~£10,000 and almost no disruption. To insulate to PassivHaus I'd have to tackle over 300 square metres of wall and floor and I doubt I could do that for £3/metre^2!

However, there is now a new range of Danfoss heat pump - the Opti range. The CoP quoted (again at 5C brine/35C outlet) is 4.8! In my situation I'd expect that to run an average of over 4.

With the RHI on top, this is a very attractive proposition.

[vtsnowedin]

I've been on the same rural wires on poles electric grid for 56 years. I agree that the majority of power cuts are in the winter for the reasons listed above and would add in ice storms that can bring down miles of line at a time and make it difficult to get repair crews to the work site. Also the degree of maintenance of the lines and ROWs can be a factor. Years back they got way behind on cutting back underbrush below the wires and that began to bite them with every little storm. They are past that now and the reliability has gone way up. Tree falls have cut my power twice this winter during wind storms but in both cases they had it back on in a few hours.
As to back up heat that does not require electricity. Nothing beats a well set up wood stove in a basement if you have the chimney and your local regs allow it. Just build a fire and open the basement door and you can keep the whole house above freezing if not comfortable in every room. Having a run of wood (1/4 cord) on hand for just such emergencies doesn't take much space.
If you have a gas kitchen range the top burners can be lit with a match when the power is off and you can heat large pots of water and that process will keep the kitchen warm even if you don't need the water. I would be nice to just put a roast in the oven but most units today will not let you light the oven with a match.

[emordnilap]

AFAIK though the pump normally runs continualy so as to prevent the small amount of water in the stove from boiling.

No, ours switches on and off; there's a small thermostat on the stove exit pipe.

[Potemkin Villager]

Pumps are just another thing to go wrong, cheap inverters are bound to go pop when you most need them. A back boiler on a good solid range and larger pipes is my preferred option.

I have recently heard several cautionary tails of people having heat pumps supplied by no longer existant suppliers expire and require replcement at great cost ditto the dreaded light sheet metal wood pellet boilers.

The prices of a lot of this dodgy kit shot up as soon as grants were avail ble.........

[JohnB]

The Hockerton Housing Association use the heat from their conservatories to increase the COP of their heat pumps but they are small ones heating their Domestic Hot Water supply.

Have they got them working again? When I visited several years ago, most had gone wrong and they weren't going to fix them.

[JohnB]

If you have a gas kitchen range the top burners can be lit with a match when the power is off

I've heard that you can only get LPG cookers with electric ignition now, and can't light them without electricity. Not very helpful if you're off grid!

[kenneal - lagger]

The Hockerton Housing Association use the heat from their conservatories to increase the COP of their heat pumps but they are small ones heating their Domestic Hot Water supply.

Have they got them working again? When I visited several years ago, most had gone wrong and they weren't going to fix them.

It was several years ago that I went there so they may have expired since. Our 2.1kW output air source heat pump expired in 1986 when the generator, who's shed it shared, caught fired and the lot burned out.

The rings on our LPG range can be lit manually but the oven won't work without an electrical connection. We queried it with the manufacturer but they said it was a safety feature and weren't interested about use when the grid was down, which can be a fairly common happening in a rural location with overhead lines. You townies might not suffer from that.

Another way of looking at this is that I have reduced my area weighted U value down from 0.54 (part old house, solid floors, solid walls) to 0.18 - near PassivHaus. I've done this for ~£10,000 and almost no disruption. To insulate to PassivHaus I'd have to tackle over 300 square metres of wall and floor and I doubt I could do that for £3/metre^2!

No you haven't! You're still wasting energy but you're not paying as much for it. In energy terms you might as well be using gas direct as, with the efficiency of generation, you would be using less energy for the amount of heat given than you are to generate the electricity. If you insulated outside you would have no disruption and a better job than insulating inside.

[vtsnowedin]

If you have a gas kitchen range the top burners can be lit with a match when the power is off

I've heard that you can only get LPG cookers with electric ignition now, and can't light them without electricity. Not very helpful if you're off grid!

Well I have a brand new GE gas range set up on LP in my kitchen. I just walked over to it and unplugged it to take it off grid and lit one of the top burners with a match. Perhaps ones sold in the UK have an electric thermocouple on the top burners like the oven does but I would think that would make it very slow to light. Try yours and see for yourself.

[JohnB]

Try yours and see for yourself.

I've only got a caravan gas hob and grill, and they have to work off grid, so light with a match. It was a discussion about people living in off grid houses trying to find a household cooker.

I hope if I end up off grid in a house I'll use rocket stoves and the like.

[biffvernon]

The rings on our LPG range can be lit manually but the oven won't work without an electrical connection. We queried it with the manufacturer but they said it was a safety feature and weren't interested about use when the grid was down, which can be a fairly common happening in a rural location with overhead lines. You townies might not suffer from that.

That's exactly our experience. We have a Rangemaster, I think it's made by Aga. The non-functioning of the oven in a power cut has been a real nuisance a couple of times.

[An Inspector Calls]

Another way of looking at this is that I have reduced my area weighted U value down from 0.54 (part old house, solid floors, solid walls) to 0.18 - near PassivHaus. I've done this for ~£10,000 and almost no disruption. To insulate to PassivHaus I'd have to tackle over 300 square metres of wall and floor and I doubt I could do that for £3/metre^2!

No you haven't! You're still wasting energy but you're not paying as much for it. In energy terms you might as well be using gas direct as, with the efficiency of generation, you would be using less energy for the amount of heat given than you are to generate the electricity. If you insulated outside you would have no disruption and a better job than insulating inside.

Yes I have!

The energy I'm now wasting is solar energy that I've extracted from the adjacent field using a heat pump. That energy would have simply been lost if I hadn't extracted it. In other words, I have my own energy farm. What is only relevant is the amount of energy I have imported, and that is on a par with PassivHaus. Where the imported energy came from is as relevant in the heat pump case as it is would be for PassivHaus.
I'm not on the gas grid.

It's well nigh impossible, economically, to insulate outside apart from gable ends, and I'm sure it would ruin the appearance of the house. And I remain very suspicious about the damp performance owhen cladding stone walls with foam insulation.

(By the way, what will happen to all this foam we're splashing around as insulation in 50 years time? The stuff's not going to last forever, it's bound to collapse to a powder).

I'll take the rare occurences of grid failure on the chin, in the same manner as those people who've struggled for oil and LPG supplies through the last winter, or have experienced difficulties with their various types of boilers. All I have is a fridge, and they're the most reliable domestic appliance. A big fridge, rather like those unreliable fridges you see in hospitals and supermarkets - always failing aren't they?

[An Inspector Calls]

Pumps are just another thing to go wrong, cheap inverters are bound to go pop when you most need them. A back boiler on a good solid range and larger pipes is my preferred option.

I have recently heard several cautionary tails of people having heat pumps supplied by no longer existant suppliers expire and require replcement at great cost ditto the dreaded light sheet metal wood pellet boilers.

The prices of a lot of this dodgy kit shot up as soon as grants were avail ble.........

Well Danfoss have been around for ages. As for spares, actually I think you're wrong. The guts of the thing contains a lot of components that are commonplace on commercial fridges and freezers, and they're readily interchangeable. Friends are getting quotes for similar systems and they seem on a par with what I paid. I haven't noticed PV panels shifting in price up or down so why should heat pumps?

[adam2]

[
The grid event you refer to was not a rota cut. It was a low frequency incident as is obvious from the title of the report:
"Report of the investigation into the automatic demand disconnection following multiple generation losses and the demand control response that occurred on the 27th May 2008"

The cause is well described therein:
"On the morning of 27th May an unrelated and near simultaneous loss of generation at Generator A (345MW at 11.34am) and Generator B (1237MW at 11.36am), totalling some 1582MW at the time of loss, gave rise to a drop in system frequency to 49.14Hz. Following this there was a further, as yet not fully explained loss, which led to a further drop in system frequency to 48.795Hz."

All very coy! Generator A was Longannet, B was Sizewell, and the "further, as yet not fully explained loss" was the wind fleet tripping because of low frequency.
.

I can not agree that the event described was not a rota cut.
Owing to the unexpected failure of two large generating units, the grid frequency fell to well below normal levels.
To prevent the frequency falling any more, a percentage of the load was automaticly dissconnected by low frequency relays.
Not enough power to go around, some load cut off. Sounds to me like a rota cut, even if only for part of one day.
It could happen again, but should be a rare event.
Regular rota cuts are unlikely but could occur, perhaps as a result of a severe shortage of natural gas, as might be caused by turmoil in the M/E.

[kenneal - lagger]

The energy I'm now wasting is solar energy that I've extracted from the adjacent field using a heat pump. That energy would have simply been lost if I hadn't extracted it. In other words, I have my own energy farm. What is only relevant is the amount of energy I have imported, and that is on a par with PassivHaus. Where the imported energy came from is as relevant in the heat pump case as it is would be for PassivHaus.
I'm not on the gas grid.

You are using additional energy to power the heat pump. With Passivhaus levels of insulation you wouldn't be using any energy at all to heat the house most of the time.

It's well nigh impossible, economically, to insulate outside apart from gable ends, and I'm sure it would ruin the appearance of the house. And I remain very suspicious about the damp performance owhen cladding stone walls with foam insulation.

You don't have to use foam insulation. There are plenty of breathable insulation systems including fibre boards, Rockwool and you could even use sheep's wool with a bit of care. You are assuming that fuel will remain affordable when talking about the economics of the situation.

Your stonework would probably be drier with external insulation as there would be less interstitial condensation in the stonework or mortar. A stone house would give tremendous thermal mass which, if warmed during the summer, could heat the house well into the winter.

By the way, what will happen to all this foam we're splashing around as insulation in 50 years time? The stuff's not going to last forever, it's bound to collapse to a powder).

It's protected from UV and weather exposure by the render covering so should last quite a while. I'm not sure what the "shelf life" is but there is no reason why it should not last the life of the house.

I'll take the rare occurences of grid failure on the chin, in the same manner as those people who've struggled for oil and LPG supplies through the last winter, or have experienced difficulties with their various types of boilers. All I have is a fridge, and they're the most reliable domestic appliance. A big fridge, rather like those unreliable fridges you see in hospitals and supermarkets - always failing aren't they?

You're assuming that the next fifty years will be like the last fifty years. A grave mistake.