Monthly Archives: May 2014

Raw Experiments

So having started to discuss whether by 2020 a portion of the 3 Billion who currently cook on solid fuels could cook with Solar Electric, we decided we should start with ourselves to see if its feasible.   The key technical issue is not whether solar can do it and will be cheap enough, but more whether deep cycle batteries will be happy with the rapid discharge.  Are they likely to fail  too quickly to make the economics work, and if we oversize them to compensate, does that mean the system is just too unwieldy.  This needs proper research from battery specialists and we will be working on that and the necessary partnership, however in the meantime Simon has set up a 12V 100Amphr battery in his kitchen, and is going to spend 2 weeks cooking all his meals with a 500W electric hob.  (Although Simon has Solar feeding into the grid on his house, due to the UK weather he is just going to recharge the battery each day from the mains)

Target consumers

We believe as many as 2 billion people across the developing world would stand to benefit from solar electric cooking. Who are these people? In simple terms, African and Asian dwellings can be divided into the following categories, each presenting a potential demand for a solar electric cooking solution:

  • Urban dwellers in formal settlements. Many of these households may have access to electric utility. Their challenge for cooking is often that the electric supply is sometimes unreliable (with load shedding), and costly. There may be a small market within these households.
  • Urban dwellers in informal settlements. These are a potentially strong market segment. Utilities often do not connect to informal settlements to avoid legitimising them. Illegal connections are often made but these are chaotic, ‘weak’ and hazardous. They are rarely strong enough to enable cooking, plus the tolerance of the utility to illegal connections is often based the fact that they consume relatively little power – if everyone started cooking, the utilities might invest more in enforcing their legal rights. The product would provide a good fit, if it were competitive with the higher grade fuels commonly used in urban areas, and it would fit urban working patterns where people eat in the evening.
  • Peri-urban conurbations. Surrounding most towns is an area where connections to utilities are not really cost effective, and households need to buy solid fuels (in the absence of ‘free’ wood resources).
  • Rural populations. The system is unlikely to get traction where collection of wood is relatively easy and free. Edges of forests are probably not the best market. However, in locations where fuelwood is scarce and it takes a significant amount of time to collect it, there may be a market for the system. Recent trends show access to fuelwood is decreasing in areas where it was previously abundant, and market prices are on the rise. Rural South-East and South Asia could be particularly strong markets.
  • Internal displaced and Refugees. In many displacement situations refugee camps have to be provided with cooking fuel otherwise the collection of wood from a concentration of people can harm the environment permanently.

Assumptions of Solar Electric Cooking

Some have asked us what assumptions have guided our beliefs in Solar electric cooking. The following are the assumptions we are making when advocating research into, and strategic deployment of Solar Electric Cooking (SEC). Some of these assumptions will be further elaborated in other posts, along with support references. More information is also available in our concept note. Any comments or suggestions are welcomed!  That’s the point of a blog 🙂


  1. 1.5 Billion spend more than $10 a month real cash on Wood/Charcoal or Kerosene.
  2. About 0.5 Billion spend more than $25 per month
  3. Solar Electric Cooking (SEC) would not, indeed need not, replace ALL cooking needs for any one household, but make substantial savings
  4. The cooking energy needs of a person are said to be an effective 2MJ per day (for electric).
  5. We assume that the 2MJ figure often cited in regards to energy requirements for cooking is not quite correct and is not an absolute.
  6. A family of 5 at 2MJ per person implies 1kW cooking for 2.5 hours – this doesn’t feel right.
  7. Many families cook one meal a day, in the evening
  8. Most meals for a family of five can be cooked in one hour on a 1kW hob
  9. SEC Lite, as a 500W system, aimed at 1 hour cooking, would have a market with smaller families and urban locations
  10. A 500W system can boil 2.5 litres in 25 minutes from room temperature.
  11. The key technical challenge is around the lifetime of the battery.
  12. A correctly sized battery could last 2 years with rapid discharging for one hour every night.
  13. Such a battery would not be prohibitively expensive, nor physically too large.
  14. The key policy and practice stakeholder challenge is about mindsets
  15. Those working on wood and charcoal stoves have had difficulty convincing people to invest $10 to $20 in an improved stove – so the idea of a family investing $200 in a system seems to them beyond practical socio-cultural reality.
  16. Those working with Solar panels had difficulty rolling out lighting systems pre LED, and perceive LED low consumption as the key that has unlocked their work – so the idea that a system could supply 1kW for cooking seems out of reach.
  17. We assume that people have not revisited the cost of the system to consider solar panel cooking in the last 2 years.
  18. Everyone seems to rely on Hankins documentation of African solar insolation which suggests there is only 6 hours sunshine?
  19. At 6 hours, the ratio of hours generating to hours consumption for a lighting system running for 4 hours in the evening is 3:2
  20. At 6 hours, the ratio of hours generating to hours consumption for a SEC system running for 1 hour in the evening is 6:1 – with implications for sizing of panels and resultant cost, giving cooking an cost ‘advantage’, which many solar lighting enthusiasts do not have at forefront of mind.
  21. Solar has come down in price dramatically in the last 3 years, and will continue in a downward trend.
  22. The tipping point for this system may not be quite yet, but by 2020 a cooking system could be installed at profit at $200.
  23. SEC at scale might make a positive difference to the local environment, retaining tress which otherwise might have become fuel
  24. SEC in refugee camps would make a very big difference to local environment.
  25. SEC at scale might have a negative effect on the local economy – displacing charcoal makers, wood sellers, stove makers, etc.
  26. SEC at scale might have a negative effect on the balance of payments – requiring foreign capital for imported equipment while wood and charcoal are a part of the local economy.
  27. SEC at scale might have a positive effect on the global environment, reducing carbon consumption.
  28. SEC has positive health benefits reducing respiratory problems.

The problem is cooking

“There is an urgent need for development agendas to recognize the fundamental role that household energy plays in improving child and maternal health and fostering economic and social development.” Torres-Duque et al, 2008

Globally there has been a huge investment for more than 30 years to find a way forward. There now seem to be a myriad of possible solutions, which fall into three broad categories:

  • transition to higher grade fuels (e.g. from biomass to gas)
  • improved efficiency (e.g. improved cook stoves for biomass)
  • solar cookers (that have varying degrees of uptake and success).

Taking these in reverse order, solar cookers have been constrained by the timing of the cooking (to coincide with the sun) and the cultural style of cooking – they work well where baking is the dominant form, but less so where other forms of cooking are the norm.

A lot of work has been done on improving biomass based stoves, including forced air, gasifiers, alternative fuels, etc. Improved cook stoves represent a promising alternative, although so far success has often been limited by  designs that are unsuitable for local customs, ineffective financing, poor distribution channels, or insufficient social marketing.

An alternative strategy is to ‘upgrade’ the fuel – to move up the energy ladder. Use of mains electricity has been adopted where it is affordable and has a measure of reliability. It is common in urban slum dwellings to find a simple electric hob or ring. However, while electric stoves are smokeless at the point of use and do not produce any emissions within a household, the actual contribution to the global environment will depend on how the mains electricity is being generated. Poor households have varying degrees of access to mains electricity, depending often on illegal connections that cannot draw too much power; supplies are also subject to load shedding and power outages implemented by the utility. As a result it is common to find kerosene and LPG gas stoves in slum areas, which, while cleaner than biomass, pose significant risks associated with fire and fumes, and also tend to be relatively expensive.

What if we could use solar cells to charge a battery during the day, and cook with it during the night, on a fairly standard cooking ring? This may not be a solution for the bottom billion, but it would perhaps address the needs of the 2 billion rising middle and upper poor.

Source: Torres-Duque, Carlos, et al.(2008), “Biomass fuels and respiratory diseases a review of the evidence.” Proceedings of the American Thoracic Society 5.5, 577-590