D Fritschen

Hello. I have had great success in making biochar with solar powered. Both with solar thermal at 350c. And solar pv to a resistive heater. Also at 350c

Why do I do this?  Because if you use solar power. Or any power then you get to collect all the syngas and synoil. Think of it like a battery:). I use solar power to make fuels during the day.  When I need diesel or cooking or heating gas I have it ready with the maximum volume possible.

Photos and details here -https://m.facebook.com/story.php?story_fbid=7743367425712373&id=187170411332150

Hello.  We here at wastefree23.org have finalized the design. I will post video of it work next week

The larger the system the better it works because of heat retention in the sand heat bank

Our application is using pv to heat sand. Then the sand to heat a pot with food. Beans rice etc.

30% of the world uses wood to cook. So everyone is better of if they can use solar

Our final solution is to braze a 1/4” diameter stainless steel tube to the outside of a pot. Low temp brazing with aluminum/zinc for heat transfer.    A little water is dropped in the tube in the sand. It turns to steam and then coils around pot. As it condenses it looses a lot of heat that goes into pot.  For a 25 gallon pot we will be able to brig that to a boil in 30 minutes.   Everything has a a lot of insulation.  The hot water from the steam stays beer the heat bank so heat loss is minimal


This system will cost about $6000 to build labor and material in the 30% of the work with low income.  Many of these 2 billion people spend $1000 or $2000 a year for wood to feed the kids at school. This system will replace that expense. And after the third year no more fuel cost:).

Plus these schools are burning 50 or 100 pounds of wood a day.  If we can install this in a few thousand schools. That is a lot of trees not cut down. And a lot of smoke not put in the air. And a lot of cooks who won’t be breathing the smoke:).  

We are boiling 100 liters a day to cook for 300 so we are using 12kw of panels because rven though the system is near the equator they city does not have many sunny days.

Since we are feeding a school full of children there can be no days with a lack of heat

We are use the coiled cooktop electric elements. When they are new they are easy to unbend and straighten out

The sand is working great for a slow cook.  The cooks who will be using this system are use to a fast heat and boil with the wood fire they have been using    To keep the cooks happy:) we are going to pump 200c oil to the area next to the pot sides and bottom to get more heat faster.  

Will post all the details next month

Hi.  I am very happy to find this chat

We are building the same thing but for schools so they can cook and not use any biomass. Schools will have zero cost zero pollution cooking

Economics on this are pretty awesome.  Schools in central Africa spend $1500usd a year. Varies greatly to feed 300 students buy wood


A sand battery cooker costs $5000 to build and will run for 20 years.


We will begin installing April 2024


The system is a cubic yard of sand mixed with shredded aluminum cans  24” of mineral wool around that.  Stucco then shreded plastic trash 24” thick and more stucco

10kw of panels.   The cooks use 25 gallons of water a day to boil beans corn rice etc.

Our system is charged to 400c in 5 days


We have 100 gallons of water I. The insulation too but in a region so it does not boil

Cook comes in uncovers the hot cooking pots adds food and adds hot water from the tanks. The pots are surrounded by the 400c sand and aluminum.  The food cooks for as long as needed. 1/2 the 25 gallons goes up as steam

The system consumes / losses about 50 kWh per day. The power from pv ranges from 16 to 80.   The sand and water storage buffers us through the cloudy days

30% of the world uses wood to cook. Expensive polluting and causes deforestation. We are working to switch the schools and institutions over to solar to save them money. Stop the air pollution and deforestation

Any suggestions please let us know!  Thanks. Dan wastefree23.org