Solar Outside The Paradigm!

I've never been a huge fan of sand batteries, but the fact remains sand IS a "dirt" cheap thermal energy storage method...

Sand by itself has very high thermal resistance and requires extremely high temperatures to store a lot of heat.

A few months ago, I made a simple sand battery experiment to heat my well house during the winter. It had a single 300w solar panel connected to a quartz tube element.

I experimented with additives to enhance the thermal conductivity of sand. One cheap method is to mix scrap metal chips (such as CNC mill or metal lathe scraps) into the sand. In one of my sand battery experiments, I mixed in aluminum shavings into the sand. They had the effect of helping heat get into the sand faster... especially bypassing the outside layer of the sand and moving the heat inwards underneath the surface.

The sand was deliberately kept beneath the heating element to track how the heat moves downward (against it's natural tendency) and "into" the sand.

This "upgrade" does work. And it's more or less cheap, but not as cheap as sand alone.

Other methods I'm interested in are graphite based, but right now I can't risk breathing the dust so I haven't tried it.

I've also tested the behavior of coarse vs. fine sand vs. water in terms of TES. Coarse sand allows more air to penetrate and also tends to let our more heat. Fine sand keeps the heat better, but sometimes that's not what you want.

In fact in my experiments I soon discovered plain old water is a great thermal storage system. Possibly better than sand - it's easier to get the heat in, and get it out again later. Plus, water can be pumped through a radiator on demand.

Still the metal chips in sand is an intriguing idea. On an IR camera, you can see how the heat moves around and the aluminium chips do help somewhat.

My next project is probably to heat my workshop using some sort of TES solution, but that's a ways down the road. If things go well enough, I will post the results here - stay tuned!

More details here: https://solarpoweredge.com/2025/11/21/heating-a-well-house-with-simple-clean-solar-electric-power-thermal-energy-storage-tes/

Why is it that most 12-volt cooking appliances today leave so much to be desired? From food "warmers" to fry pans that seem to be intended to last about 2 days before they break (or melt, or catch fire), the selection is not too encouraging. These appliances tend to be very weak, low quality and usually more about "warming" food than actually cooking it.

12 Volts is truly the universal voltage - it's every where.

Why can't 12-volt cooking appliances that are actually "kitchen grade" exist? The answer is: there is NO REASON WHY NOT!! Kitchen grade means built just like the AC 115/230v appliances we all know. Metal construction, safe design, affordable, reliable. Easy to use. Lasts for many years.

Is 12 Volts DC too weak to actually cook anything?

NO, I have disproven that silly myth long ago. I always knew it was possible.

Here's one of my 12V cooktop prototypes boiling a pot of noodles with 2x20ah LiFePO4 batteries:

Here is one of my smallest 12V mini ovens which can bake bread, cook vegetables and more using only about 150 WATTS:

Basically, with good appliances a simple 12V automotive battery can cook a family's meals for many years, with NO inverter, NO high voltage and NO fuel burned.

No, these appliances don't have to be small. Behind the scenes, I have built many other low voltage DC cooking appliances, including larger and more powerful ovens that run on 12, 24, and 48V DC. If some sad guy in his workshop can build them... then so can ANY factory!

Tasty! A tiny 12 Volts Battery Did This:

When you add one or more 100-watt solar panels to a 12V battery and these appliances, suddenly things start to change. This is a simple way to cook food for decades to come. Why isn't such simple tech on every store shelf, and available to every human who needs it? This lack of low voltage DC appliances has appeared glaringly obvious to me - even going back years, and before I tried to follow up on any of the ideas.

Times Will Change

Trouble has been increasing. Things are getting more complicated. Cooking food is critically important for health, survival and morale. And yet, it's taken for granted by many.

What happens when "the system" collapses (maybe a Grid Down scenario) or undergoes a severe blow? What if your grid-powered oven no longer works? The top-heavy overly technological ecosystems which are so popular today can suddenly become a liability at best, and compeltely useless at worst.

But I'm Off Grid, Man!

You use the Grid every single day! You run your house on technology that came from the grid. Charge Controllers. Logistics. Internet, E-commerce. Batteries. Communications. Services. Food. Gasoline. All grid powered.

This is the truth. True off grid means being prepared and having the right mindset, whether your house runs on batteries or not. You might be "off grid", but what if your inverter burns out and you can't power anything and can't order a new one?

Think ahead! Think of others! We all go down together, if we don't become more proactive together. Seeking and embracing simpler, more robust electric cooking and appliances will benefit the whole world in the long term. Once these ideas become established, it opens the door for the market to respond and start providing new options.

Remember, everything came from the grid, including your T-shirt, shoes and that fancy inverter with a hidden bluetooth link that makes it vulnerable to remote shutdown. I don't know about you, but even though I have inverters and off-grid solar power to run any appliance I need, I still like having simple backup plans in place in case this happens. And besides, people all over the world need alternatives too.

And that's in fact why our house is already migrating to a pure-DC off grid power system. I don't hate inverters, but I really don't want to be 100% dependent on such a grid artifact.

Thinking Of People Other Than Ourselves

In some parts of the world, they can't afford a fancy off grid solar power system. Maybe they could get their hands on an old car battery and a 100 watt solar panel, but not much else. A simple 12 volt cooking appliance would make their day! For years.

The world already needs alternatives right now. 12 Volts is everywhere. Anyone can find a 12 volt battery under the hood of a car and cook their meals - except they can't because nobody seems to care about it. And yet, I am approached constantly by people who are 100% interested in the concept, yet they have zero access to affordable, kitchen grade 12V appliances. All they can find are the cheap plasticy excuses for 12V appliances that have always been available. And some of them can't find any options at all.

Doing Something About It

I certainly already am - for years. I have manufactured many different 12v appliances with my own hands. Also, I produced a dedicated video showing people HOW TO CONVERT a standard toaster oven to 12 volts - with simple hand tools and DIY skills! If you don't feel comfortable doing that, TEAM UP and share the knowledge!

DIY - Do It Yourself! My hope is that soon, affordable, robust and kitchen-grade 12 volt cooking appliances will appear on store shelves. They should not much more than their AC grid powered counterparts. Sure, there needs to be a bit more safety integrated into the design, but 90% of the contents of these appliances are universal no matter what voltage source is powering it.

I'm not alone. Over the years, I've met a few people who want to solve this lack of DC appliances. Hopefully, it will happen! Edison Was Still Right - DC (direct current) is coming back!

Believe It Or Not! Off Grid in the 1900s

Before the centralized electrical utility power grid took over completely, many farms and houses were completely off the grid using PURE DC in their houses in the 1900s. These systems were based on 32 Volts DC distributed to residential wall outlets, and they were powered by a rack of lead-acid batteries.

This was before solar panels - so charging was done with a small gasoline generator and/or a windmill (wind turbine). They had every kind of appliance: coffee makers, clothes irons, water pumps, washing machines, radios, lights, vacuum cleaners, fans, you name it.

Unfortunately, this history has been all but wiped out from the archives. It's so hard to find detailed information about these systems any more. What a shame.

The 32V DC systems powering our ancestors' homes were part of what motivated me to take the journey of powering my house with pure DC solar - right down to the wall outlet. And this system needs no inverter and no charge controller. I have been on this journey for several years now, inventing everything from scratch including my own appliances, safety standards, load centers, protection systems and more.

Why not make off grid solar more powerful, more streamlined, simpler, more affordable and more robust for the world at large? There are so many people worldwide who could benefit from this simple and robust technology.

This system design is grid down friendly too. Simple contactor switches, analogue gauges and simple resistance heat sources don't care about EMP very much!

Safety and Lower DC voltages

While 32 volts is quite safe, I decided to go with a higher voltage in my system - 55 volts nominal. This voltage is at the "edge" of the upper end of "safe". The problem with higher DC voltages above 55 volts is they can penetrate the skin far more easily and into the nerve pathways. I believe 55 volts is a good balance between running powerful loads and still maintaining safety. Plus, it's directly compatible with standard 51.2V 16S LiFePO4 battery modules, and many 48V off the shelf DC appliances. Engineering is about picking the best pros and cons for the design requirements, and building good systems that will meet the needs of humankind.

Direct Drive PV DC Capability

The 55V system, I designed is totally off grid powered by direct-drive PV-DC (PV-to-load or PV2L for short). What makes it even more unusual is that the battery is OPTIONAL! The battery is normally kept switched out of circuit during the day, and all wall outlets are served by direct DC solar power. Even with NO battery, or if the battery fails, the system will still work during the day from PV Solar Power - cooking, heating, lighting all without batteries. Fault tolerance and resilience.

Edison Was Still Right - DC Is Coming BACK

Let's bring Direct Current back again - the world doesn't know what it's been missing! Solar power has become so complicated and tedious today, and there ought to be more choices for those who cannot afford an expensive and complicated off grid installation.

I will be posting more on this topic in the future. Below is an existing video presentation demonstrating our 55V residential off grid DC system (it includes a short segment discussing the 1900s 32V systems). There is also at least 2 blog articles, here, and on our other blog site solarpoweredge.com (linked below).

Article written by Dave, Solar Power Edge channel www.solarpoweredge.com (C) 2026 All Rights Reserved - We Reserve All Rights

Our 55V DC Load Center:

55 Volts DC - Powering Our Kitchen Cooking Needs 24x7:

The system also heats our house:

An earler video I made about the 55V DC system and it's past development:

Link to a post about our 55V DC System on our other blog:

In my workshop... a mini BLDC air conditioning compressor spinning up on a single 100-watt 12v solar panel - no battery.

I built a 100% direct PV-DC solar window air conditioner unit that uses simple 100-watt commodity solar panels to power it. No battery needed. The unit was built from scratch using off the shelf parts and R134a refrigerant. It is part of my continued research and development of pure DC off grid solar systems.

After years of experiments, testing and development, we are powering part of our house with 100% off grid DC. No charge controller, no inverter.

Heating, cooking, lighting and other appliances are in use primarily. We're now working on a DC heat pump solution.

This kind of system can also run off of direct PV DC - meaning the solar panels are powering all house loads directly. The battery is optional, and if present, is switched into standby during the day when it's not needed. Multiple buildings are linked together forming a DC micro grid.

100% DIY, simple, streamlined, more affordable - that's the way solar should be! We will be posting future updates on our blog https://www.solarpoweredge.com