navitron
 
Renewable Energy and Sustainability Forum
Welcome, Guest. Please login or register.

Login with username, password and session length
News: Anyone wishing to register as a new member on the forum is strongly recommended to use a "proper" email address - following recent spam/hack attempts on the forum, all security is set to "high", and "disposable" email addresses like Gmail, Yahoo and Hotmail tend to be viewed with suspicion, and the application rejected if there is any doubt whatsoever
 
Recent Articles: Navitron Partners With Solax to Help Create A More Sustainable Future | Navitron Calls for Increased Carbon Footprint Reduction In Light of Earth Overshoot Day | A plea from The David School - Issue 18
   Home   Help Search Login Register  
Pages: 1 [2]   Go Down
  Print  
Author Topic: Well insulated slow cooker?  (Read 15825 times)
Robl
Jr. Member
**
Offline Offline

Posts: 63


« Reply #15 on: January 22, 2012, 09:16:18 PM »

We bought a new elec cooker 6 months ago.  I chose on the basis of best efficiency - the new one has a triple glaze front door, and is insulated around the oven.  It uses about 1KWh to cook a chicken - so long as you keep the door closed, the oven stays at temperature for ages without the heater element being on.
It beats our old one (12 yrs old) hands down - that had no insulation at all, you could feel a warm draft of air from the back of it all the time it was on, and the 1.8KW heating element was on almost continuously to hold 180C temperature inside it.
I'm sure the same can be true of slow cookers - good & bad ones, it's all about the insulation, not the element power consumption.     
Logged
M
Hero Member
*****
Offline Offline

Posts: 4773



« Reply #16 on: January 23, 2012, 07:43:00 AM »

Don't want to disagree with everyone, but those watts sound high. We got a slow cooker in the summer to go with our PV, it has high, low, and stay warm.

The high is approx 150w, low 100w, (checked via energy monitor) we've found that cooking times are generally less than most recipes state. Eg if recipe say's 5 hours high, we find 5 low will do the job.

Generally we cook most meals (if in) 1 hour high, then about 4 low, so costs 500w to 800w. All within the PV time window, though during winter, not necessarily whilst generating enough when including background consumption.

The big plus though is that the meat is simply unbelievable! Couldn't find a knife one day, so dished out a pork joint with a fork and a spoon! At this rate, I'm in danger of de-evolving my teeth.

Mart.

PS We cover the top with a light tea towel, partly to keep some heat in, but mostly to stop the lid rattling when the pot is bubbling.
Logged

Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
stannn
Global Moderator
Hero Member
*****
Offline Offline

Posts: 4611



« Reply #17 on: January 23, 2012, 12:43:53 PM »

Which model did you buy Mart?
Stan
Logged

2.45 kWp PV (Navitron supply), 40 evacuated tubes (Navitron supply), Clearview 650 log burner with back-boiler heating cottage and water, 2 off 50W border collies, 1 off 35W cat, 1 off 25W cat.
melweb
Newbie
*
Offline Offline

Posts: 18


« Reply #18 on: January 30, 2012, 02:02:46 PM »

I bought one of these from Tesco about 18 months ago (cheap & cheerful for a tenner I think). I have to agree with Mart, meat is so much better than a conventional oven. Even my two boys say that my spareribs are as good as TGIF! Bought it after I'd had the pv installed to make use of the free leccy.
Logged
M
Hero Member
*****
Offline Offline

Posts: 4773



« Reply #19 on: January 30, 2012, 02:10:09 PM »

Which model did you buy Mart?
Stan

Sorry Stan, didn't mean to ignore you, missed this post.

Wifey bought a Breville ITP136

I think she said it cost about 12? It says 210W on the bottom, but doesn't seem to use that much. Looking at it now, it is 'smallish' so maybe my surprise at others energy consumption, is that their's are bigger than mine (so to speak).

M.
Logged

Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
stannn
Global Moderator
Hero Member
*****
Offline Offline

Posts: 4611



« Reply #20 on: January 30, 2012, 02:36:28 PM »

Thanks Mart
Stan
Logged

2.45 kWp PV (Navitron supply), 40 evacuated tubes (Navitron supply), Clearview 650 log burner with back-boiler heating cottage and water, 2 off 50W border collies, 1 off 35W cat, 1 off 25W cat.
Mike McMillan
Full Member
***
Offline Offline

Posts: 200


« Reply #21 on: January 07, 2018, 08:04:10 PM »

I bought a second hand crock pot early in 2017, thinking it had to be perfect for cooking with PV. As per the above comments, I was appalled by the lack of insulation. I started experimenting by covering it in towels, cooking high for an hour, after which it went into warm mode. It worked a treat, and I kept a log of how long it stayed on high before switching to warm. A whole chicken sitting on a wire grill in the ceramic pot with no water, was absolutely superb. Unfortunately, I inadvertently left it on high for 4 hours and of course melted some of the electronics.....
i would like to try gain, but cannot find any that have a thermostatic control. How simple would it be to retro fit one?  Anyone tried it? It is the way to go, using 250 watts for an hour and then almost nothing.

Mike

Osborne Bay
Logged

Off grid; 4KWH install charging Rolls 24v 1000 A.H. batteries with 3 Tristar controllers. 3KW Victron Inverter with FIT meter on output. Relay driver automatically opens circuits as battery charges. 6 x 15 experimental solar collectors feeding 250 L. tank.  Angus wood gasification boiler.
Mike McMillan
Full Member
***
Offline Offline

Posts: 200


« Reply #22 on: June 22, 2018, 06:22:44 AM »

As a follow up, I have just bought another second hand very cheap crock pot. I still cannot see an insulated slow cooker with a thermostat installed with a google search. crazy. Anyone have an idea of a suitable thermostat switch I could install on it??

Mike

Very dry and sunny Osborne Bay
Logged

Off grid; 4KWH install charging Rolls 24v 1000 A.H. batteries with 3 Tristar controllers. 3KW Victron Inverter with FIT meter on output. Relay driver automatically opens circuits as battery charges. 6 x 15 experimental solar collectors feeding 250 L. tank.  Angus wood gasification boiler.
Mike McMillan
Full Member
***
Offline Offline

Posts: 200


« Reply #23 on: June 22, 2018, 06:46:10 AM »

Maybe something like this?



Logged

Off grid; 4KWH install charging Rolls 24v 1000 A.H. batteries with 3 Tristar controllers. 3KW Victron Inverter with FIT meter on output. Relay driver automatically opens circuits as battery charges. 6 x 15 experimental solar collectors feeding 250 L. tank.  Angus wood gasification boiler.
Mudman
Full Member
***
Offline Offline

Posts: 213


« Reply #24 on: June 22, 2018, 03:08:18 PM »

We bought a new elec cooker 6 months ago.  I chose on the basis of best efficiency - the new one has a triple glaze front door, and is insulated around the oven.  It uses about 1KWh to cook a chicken - so long as you keep the door closed, the oven stays at temperature for ages without the heater element being on.
It beats our old one (12 yrs old) hands down - that had no insulation at all, you could feel a warm draft of air from the back of it all the time it was on, and the 1.8KW heating element was on almost continuously to hold 180C temperature inside it.
I'm sure the same can be true of slow cookers - good & bad ones, it's all about the insulation, not the element power consumption.     
what make is it? i was dismayed to find how inefficient electric cookers are when we replaced ours. its probably the biggest single user of electricity in our flat.
Logged
Mike McMillan
Full Member
***
Offline Offline

Posts: 200


« Reply #25 on: June 22, 2018, 06:52:47 PM »

It's a basic crock pot. Only uses 150 watts, but of course, most of that is going into the room! Very wasteful, especially as it's roiling hot right now.

Mike
Logged

Off grid; 4KWH install charging Rolls 24v 1000 A.H. batteries with 3 Tristar controllers. 3KW Victron Inverter with FIT meter on output. Relay driver automatically opens circuits as battery charges. 6 x 15 experimental solar collectors feeding 250 L. tank.  Angus wood gasification boiler.
Robl
Jr. Member
**
Offline Offline

Posts: 63


« Reply #26 on: June 23, 2018, 11:02:25 PM »

Hi Mudman

Ours is a Hotpoint HUD61G elec oven/gas hob, and gets an "A" rating for it's 0.91kWh/cycle and 0.76kWh/cycle (it has 2 ovens).  I don't know what a "cycle" is, before you ask!
There's loads of ovens now that get an A, even A++ I see.  The hob isn't rated, which is kind of fair enough.  Mind you the actual kWh/cycle seems similar for A, A+, A++, not sure whats happening there - maybe it's based on kWh/cycle/litre or somesuch.  The A++ one I found was AEG BSE892330M, quadruple glazed, 0.89kWh/cycle, but a large single oven - I'm guessing that boosted the ratings.
I think there's been a huge energy use improvement over the last 10-20 years, and I'd focus on the kWh/cycle rather than A/A++, as cooking for 4 I see oven size as generally irrelevent.

Rob
Logged
Philip R
Hero Member
*****
Offline Offline

Posts: 1210


« Reply #27 on: June 24, 2018, 10:56:53 AM »

Thermostats are not suitable controllers for cooking pots because the variability of what can cooked. Boiling an egg in water at 100 Dec C, Boil or simmer, depends on the heat input . Still the same temperature. In this case, the upper temperature is controlled by the boiling point of water at atmospheric pressure. Therefore can not  use a thermostat, as its control hysteresis is too wide. For say a chip pan or pressure cooker, a thermostat might work.
Older British electric hobs used simmerstats to alter the on off duty cycle of the heater.These worked quite well.
With gas, you turn the flame up or down,even better. Modern induction hobs have excellent variability of power output.

Getting back to slow cooker pots.  If highly insulated, it will be harder to control the simmer with fixed wattage heaters, especially with the -6/+10% mains voltage tolerance and V squared power ratio of the heating element.
So for a small crock pot, the power output could be controlled using say a phase controlled energy regulator, like a 400w rated light dimmer( suitably mounted, earthed and fused) into the input lead of the cooking pot. This presumes that the pot has not electronic controls wihin, say except a simple latched over temperature cut out.
Anyone got a variac, could use that instead, although not suitable for a kitchen, health and safety no-no!
Philip  R
A few weeks ago, one of my customers was cooking up a brisket beef casserole in his slow cooker, looked very good.
It bought home the energy innefficiency of home cooking.
I recall seeing a clip on the box, of a guy who made an insulated oven and roasted  a chicken using a 60w candle filament lamp.
Look in the back of most gas and electric ovens. There is not much insulation thickness.
Logged
M
Hero Member
*****
Offline Offline

Posts: 4773



« Reply #28 on: June 24, 2018, 11:24:14 AM »

Slightly off-topic, but there is also the cooking method of heating the pot (casserole dish perhaps) to a high heat, then just leaving it to slow cook wrapped in a big duvet.

Here is the first link I could find, as searching for duvets and cooking pots just gave me loads of links to big department stores!

The Wonderbag is an electricity-free slow cooker that can slow deforestation, reduce violence and make a hearty stew!
Logged

Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
Mike McMillan
Full Member
***
Offline Offline

Posts: 200


« Reply #29 on: June 25, 2018, 07:48:45 AM »

Thermostats are not suitable controllers for cooking pots because the variability of what can cooked. Boiling an egg in water at 100 Dec C, Boil or simmer, depends on the heat input . Still the same temperature. In this case, the upper temperature is controlled by the boiling point of water at atmospheric pressure. Therefore can not  use a thermostat, as its control hysteresis is too wide. For say a chip pan or pressure cooker, a thermostat might work.
Older British electric hobs used simmerstats to alter the on off duty cycle of the heater.These worked quite well.
With gas, you turn the flame up or down,even better. Modern induction hobs have excellent variability of power output.

Getting back to slow cooker pots.  If highly insulated, it will be harder to control the simmer with fixed wattage heaters, especially with the -6/+10% mains voltage tolerance and V squared power ratio of the heating element.
So for a small crock pot, the power output could be controlled using say a phase controlled energy regulator, like a 400w rated light dimmer( suitably mounted, earthed and fused) into the input lead of the cooking pot. This presumes that the pot has not electronic controls wihin, say except a simple latched over temperature cut out.
Anyone got a variac, could use that instead, although not suitable for a kitchen, health and safety no-no!
Philip  R
A few weeks ago, one of my customers was cooking up a brisket beef casserole in his slow cooker, looked very good.
It bought home the energy innefficiency of home cooking.
I recall seeing a clip on the box, of a guy who made an insulated oven and roasted  a chicken using a 60w candle filament lamp.
Look in the back of most gas and electric ovens. There is not much insulation thickness.

Thanks for a very clear explanation. I guess I just keep bleeding heat into the room, or build a hay box!

Mike

scorching Osborne Bay, (you could fry an egg on the rocks right now)
Logged

Off grid; 4KWH install charging Rolls 24v 1000 A.H. batteries with 3 Tristar controllers. 3KW Victron Inverter with FIT meter on output. Relay driver automatically opens circuits as battery charges. 6 x 15 experimental solar collectors feeding 250 L. tank.  Angus wood gasification boiler.
Pages: 1 [2]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.20 | SMF © 2013, Simple Machines
SMFAds for Free Forums
Simple Audio Video Embedder
Valid XHTML 1.0! Valid CSS!