- 1st July 2019
Dr Jon Leary & Dr Simon Batchelor
HIVOS and the World Future Council have published a new report in their Beyond Fire series (Couture and Jacobs), which focusses specifically on the opportunity for electric cooking. The new Beyond Fire makes an extremely strong case for the transformative potential of solar electric cooking and electric cooking on mini-grids and the steps needed to develop them into mainstream solutions.
This fits well with the focus of the MECS programme, and its great to see another group thinking along the same lines and building on Leach and Oduros’ (2015) work (Prof. Leach of University of Surrey is a theme lead to MECS). Taking the time to read through the full report is highly recommended, as in this article, I only focus on one aspect – some of assumptions made to calculate the energy demand for cooking on efficient electric cooking appliances might be open for debate.
In their original report, Couture and Jacobs look at 4 pathways to achieve truly sustainable cooking: biogas, renewable power2gas, solar electric cooking & electric cooking on mini-grids. Their original report concluded that the electric cooking pathways yielded the greatest co-benefits by simultaneously enabling electricity access for other low power applications. However, in that report they seemed to us to underestimate its potential from an economic perspective, firstly by focussing solely on hotplates and not considering efficient appliances, and then further, not taking into account the declining cost trends of the key components. In contrast, Leach and Oduro’s work was considering the emerging opportunity by showing both current (2015) and 2020 cost projections (see our blog on the first Beyond Fire for a comparison of the two models).
Fortunately in this updated version the biggest changes from their 2016 report are that, following the Leach and Oduro (2015) predictions, the price points of key components (solar PV and battery storage) have now decreased (actually even further than expected) and they have become aware of the impact that energy-efficient appliances can have, in particular the EPC.
Whilst Beyond Fire (2016) perhaps understated the opportunity for eCooking solutions, I do wonder whether they may have gone too far the other way in Beyond Fire (2019). Couture and Jacobs are now comparing hotplates with 3 efficient electric cooking appliances: the induction stove, the slow cooker and the EPC. Figure ES-1 from Beyond Fire (2019) below summarises their modelling results for each appliance. They (in my view) rightly conclude that induction stoves make limited savings over hotplates, and we have learnt that this is because the biggest savings come from insulation, which is what slow cookers and EPC rely on. However, I do think the energy savings of slow cookers and EPCs might be a little over stated for the following reasons:
- The hotplate specs have become unrealistically power hungry
- EPCs and slow cookers cannot cook all foods
- EPCs, hotplates and slow cookers cook at different speeds, so would be used for different amounts of time each day
- The EPC energy consumption figures are optimistic
The hotplate specs have become unrealistically power hungry. Instead of Leach and Oduro’s 500W hotplate with 70% efficiency, Couture and Jacobs model a 2kW hotplate with 50% efficiency. They point to a YouTube video (Lovelands 2018) and a blog (Wirfs-Brock and Jacobson 2016), neither of which seem to justify these numbers. However, our cooking diary studies suggest that when you start to include behavioural factors such as forgetting to turn the stove off and preheating a hotplate with high thermal mass, then losing 20% points seems entirely realistic. However, I question whether anyone would ever seriously consider using a 2kW hotplate on a solar home system. Since most plug-in single hotplates designed for grid-connected (i.e. with no energy efficiency features) use only 1kW, this is like designing a solar lantern with a 100W incandescent lightbulb!
Just a side note here – we are increasingly aware that the old way of talking about stove efficiency is a distraction. Water boiling tests were good for charcoal stoves, because once lit the stove remains on for the duration of the meal. But for both LPG and electricity, the degree of control is much more. Indeed, as Couture and Jacobs describe so well, EPCs minimise energy consumption by spending most of their time switched off once at pressure. The ‘system efficiency’ becomes how much energy does it take to cook a tasty meal – and that depends not only on the conversion efficiencies for the fuel, but also on the skill of the cook and the efficacy of the cooking utensils, in particular the rate of heat loss from the pan.
EPCs and slow cookers cannot cook all foods. The report states that slow cookers and EPCs “may not be suitable for all meal types”, yet the scenarios presented seem to compare the appliances as if users were doing all their cooking on them. Our cooking diary research in Kenya (available here soon, see snapshot below for a sneak preview) suggests that EPCs are capable of cooking 60-80% of popular dishes, with those requiring a shallow pan or manual heat control (e.g. chapati or mandazi) not possible on most models available on the market today. Whilst we didn’t specifically study slow cookers, they cannot fry at all and can only boil very slowly, which implies that most households would struggle to even reach 50% of dishes. A more realistic 100% electric cooking scenario would be to complement the EPC or slow cooker with a hotplate or induction stove to cook the remaining dishes.
EPCs, hotplates and slow cookers cook at different speeds, so would be used for different amounts of time each day. Beyond Fire’s (2019) modelling is based on 2 hours of cooking per day, however as the name suggests, slow cookers do not cook as quickly as hotplates and EPCs actually cook faster. As a general rule of thumb, our cooking diaries studies and eCookBook have shown that EPCs can cook long boiling dishes in half the time of a hotplate or induction stove. In contrast, informal tests in our kitchen laboratory suggest the slow cooker takes twice as long as a hotplate. Quick frying dishes such as eggs or leafy vegetables take roughly the same time on a hotplate and an EPC. They may be possible to cook on a slow cooker, but it is unclear as to whether the finished product would be acceptable as steps such as browning onions would be challenging.
The EPC energy consumption figures are optimistic. Finally, whilst physically possible, the EPC energy consumption figures seem optimistic for a real kitchen scenario. It is true that when cooking efficiently with an EPC, the majority of energy is used in pressurisation. After this point, only small amounts of power are needed every 10-15 mins or so to maintain pressure, as EPCs are insulated. However, in the real world, most users also want to fry, which uses full power constantly. Reducing the soupiness of stews at the end of cooking also uses full power, so does re-pressurising after checking to see if the food is done. At the end of our cooking diaries study in Kenya, we asked each participant to cook one of the most energy intensive dishes, githeri (beans & maize stew), in their EPC as efficiently as possible. As you’ll see from the chart below, only 1 person out of 19 managed to beat the figure that Couture and Jacobs quote as an average consumption for 1 hour of cooking on an EPC (0.164kWh). What is more, the figures they quote for 2 and 4 hours of cooking are just 0.221kWh and 0.334kWh respectively (see Table 13 from Beyond Fire below). This may be possible if the EPC is not opened at all throughout the 2 or 4 hour period, but this would mean that you would only be able to cook one dish in the entire day. If it were the 4 hour scenario, that dish would have to be soup, as I don’t know of any food that wouldn’t turn to mush after that long in an EPC!
So to conclude, it seems that in a more realistic scenario for 100% electric cooking (where people cook the dishes they can with an EPC and use an induction stove or even a hotplate for those that they can’t) would likely sit somewhere between the bars for efficient and inefficient appliances in Figure ES-1 from Beyond Fire. However, it is difficult to know exactly where, as in addition to energy demand, peak power is also a consideration in system sizing. However, our cooking diaries studies and kitchen laboratory experiments to develop our eCookBook have shown that 1kWh is a realistic figure for daily energy demand for households cooking efficiently with efficient cooking appliances. 1kWh is the figure used by Beyond Fire to model households cooking on induction stoves for 2 hours per day.
Fortunately, the authors of Beyond Fire acknowledge that this is exactly the kind of information that is needed to improve the accuracy of their modelling, as their fifth recommendation is:
“Governments and donors around the world need to fund a greater range of R&D projects, including projects to demonstrate the viability of sustainable cooking solutions. Such initiatives could focus specifically on providing further analysis of cooking with different electric appliances such as slow cookers, pressure cookers and even infrared cookers, analysis of the behavioral and cultural acceptance of slow cookers and pressure cookers, as well as to support the scale-up of new business models in the cooking sector. These kinds of projects can be extremely valuable in order to gather cost and performance data, analyze behavioral and other challenges, while driving further technological innovation and cost reduction.”
This is exactly where MECS begins. You can find the outputs to date from our behavioural and cultural research on cooking with electricity, including the quantitative results from the cooking diary studies, here. To date, we have studied 4 countries in depth (Kenya, Zambia, Tanzania and Myanmar) and under the MECS programme, we shall soon have data for many more. However, let me reiterate, this is a great report, a fascinating read, and while I may challenge one or two of the assumptions, it nevertheless is a great piece of modelling that supports the key proposition of MECS – that now is the time to look beyond biomass for cooking and consider electricity as a modern energy cooking service that can offer a truly sustainable pathway to moving beyond fire.