Hans-Olof Nilsson is a Swedish engineer from the refrigeration industry who may be a retiree by age but in no way so by virtue – instead he decided to go off-grid with his house in a serious way, storing the summer sun as hydrogen to keep warm in the cold Swedish winter. On a cool, clear and sunny day, he kindly granted me a visit to his astonishing +500 square meter villa, 10 kilometers out of Gothenburg. 

By Michael Jensen, Technology Journalist

It’s 9 AM and I just left the Scand Lines ferry arriving from Elsinore in Denmark (the hometown of Shakespeare’s Hamlet). I board the X2000 train at Helsingborg Central Station in Sweden on a chilly but brilliantly clear spring morning. Soon the all-electric train hits it’s cruising speed of 200 kmh and only 1 hour and 45 minutes later I get off in Göteborg (Gothenburg) where Hans-Olof waits for me. He is a gently looking man with lively blue eyes and a trusting appearance. If he was to repair my home-appliances I would feel the enterprise was in safe hands with him. Being an electrical- and telecommunications engineer he probably would be able to fix most of them. 

After a short stroll from the station, we arrive at the parking lot, where his white electric Renault Zoe is parked. As we get in, we praise the weather and converse on the flexibility of the digital city parking system and when driving the conversation quickly changes to the pros and cons of hydrogen versus methanol as energy carriers. Bring together a couple of energy nerds and the subject will soon change from trivial matters to how to save the world.

Hans-Olof Nilsson’s house as seen from its Northward façade. His electric Renault Zoe in the foreground and an advanced weather station on top of the roof. Solar PV-panels are on the Southward roof.

The grey villa covered in ceramic tiles and three stories high (8 meters), makes quite an impression as we enter the driveway from the North. Coming in from this direction there are no solar panels to be seen yet. The Zoe comes to a halt, Hans-Olof plugs in the charging cable, and we walk on the inch-sized granite rocks around the house where I am to get my first impressions of the house’s primary energy source – the solar panels.

The entire Southward roof is covered with photovoltaic and thermal solar panels. It’s the thermal panels in the middle. The 140 square meter PVs produce 20 kWp electrical power and the 20-square meter thermal panels, 13 kW of thermal power. On the façade, right, vertical PV elements (0.8 kWp) that capture the low angle sun (12-15 degrees over horizon) in the wintertime. The pebbles are to be removed and soil will be filled up to the metal listing below.

Obviously, it’s the southward roof that delivers most of the electrical energy for the house, while on the West façade two solar panels capture the late afternoon and evening sun, producing roughly 2.0 kWp

The areas circumscribing the house reveal that Hans-Olof’s project is still in progress. A carport will be placed on the eastern side of the house and the remaining terrain will be leveled and covered with grass, except for the driveway and parking areas close to the house that will be paved with concrete and tarmac. The house itself, now two and a half year in the making, is basically done by now, with a few of the technical installations to be updated in a near future. More on that later.

The outside walls are covered with ceramic tiles from German manufacturer Tonality. They’re mounted on vertical metal rails and leave about an inch’s space to the insulation material beneath, providing for affluent ventilation and avoidance of moisture buildups in the construction. Touching the tiles, they feel surprisingly cool despite the sun’s power, now close to noon. These qualities are not accidental. Hans-Olof chose the tiles because they offer superb ventilation and heat repelling in summertime thereby reducing the need for cooling indoor. This climate shield is virtually maintenance free.

Ceramic tiles from German manufacturer Tonality make a heat repelling, well ventilated climate shield on the construction. There is about an inch of freely moving air between the insulation and the backside of the tile. As an added benefit this free space makes it very easy to draw and hide cables for exterior installations such as lamps or cameras.

Having ambled the lot to inspect the exterior installations we aim for the front door on the Northern side. Hans-Olof taps the security system’s keypad with the required combination causing a gentle welcome tune accompanying the confident click of the lock barrel turning.

Shoes off, it’s a pristine tile floor in the entrance hall. A shrill shriek very unlike the smart home salute greets us. It’s two green Amazon Parrots welcoming their master. Remembering a friend’s jealous male parrot with a dominant character and a strong beak to back it up, I quickly scan the surroundings to locate the birds. These particular specimens, moving their heads up and down with curios gazes, however, seem to be very docile and gentle on their branches.

Now with a perceived threat reduced, we can continue our tour. Birgitta, Hans-Olof’s wife, sits by her work table on the balcony of the second floor – the house is almost one open space only. She’s the architect and designed the layout and construction of the house. The living room goes all seven meters or so up to the angled ceiling where large slowly rotating fans afford an even and pleasant temperature in the huge room.

A good hour into my visit we are getting closer to the central question – how many and what type of installations are required to run a house this size off-grid? As thrilling as that answer may be – one question rises above all other – how much does is cost to go off-grid? Well, I could keep the suspense to the end of this article. The answer, however, is so amazing that I probably will keep your attention anyway if I reveal it now.

“A typical high-rise building in Sweden costs in average 32,000 Swedish kronor (3,690 USD) per square meter, our house costing in total 15 million SEK and occupying 500 square meters comes out at 30,000 SEK per square meter.” Hans-Olof says.

That’s an impressively low number considering the quality materials used everywhere plus PV- and thermal panels, as well as a significant number of control units, inverters, tanks, etc. of which we will hear more later. All units and appliances are more or less interconnected, by wire or tubes or both – totaling 15 kilometers of tubing and 150 kilometers of electrical wiring. All switches (main plugs) in the house go to a central switchboard (one of the total seven in the house) in the basement and can be individually programmed and monitored by the KNX system.

But let’s not dive too deep into the technical details now, instead we continue our tour.

Hans-Olof and I move on to the indoor-garage that holds up 55 square meters of the ground floor. Here a BMW i3 is parked for charging. With the i3 and the Renault Zoe, Hans-Olof and Birgitta have two electric cars for daily commuting plus a conventional modern Volvo for the long trips as well. The house produces enough electricity for both cars to be charged daily. Hans-Olof plans to replace the Volvo with a fuel cell Toyota Mirai. In the current energy setup, the house produces a surplus 800-1000 Nm³ of hydrogen a year – enough to drive the Mirai an estimated 10,000 kilometers annually.

In the garage, we find the spiral staircase to the basement, the heart of the house’s energy system. Things will get a bit technical from here on, so please fasten the seatbelt and brace yourself as we are going on an exciting trip through a most advanced control- and production room for the whole insular energy system. 

1. The Electrical System

The power central where PV-power (Photo Voltaic Power) comes in and is distributed to battery charging, to water electrolyzing and the internal electric grid of the house. The yellow boxes are combined inverters and chargers. They charge the batteries when surplus PV-power is available and deliver AC-power back to the house grid, drawing from the batteries, when PV-power is not available. Batteries are placed on the other side of the wall. Each box can charge with up to 8 kW effect. The grey boxes (12 kW each) above, right, are inverters only (not chargers) covering the immediate AC-power needs of the house and when sufficient PV-power is available any surplus effect is channeled to the yellow boxes charging the batteries. Each grey inverter relates to three of the yellow boxes and comprise a redundant system. In this way both inverters are working independently delivering energy to the house. The red box is a 3-kW inverter for the façade PV-panels feeding directly into phase 2 of the house grid’s three phase AC-system.

Battery storage, type lead-silicon, capacity 144 kWh – enough for running the house for 5 full days including heat but excluding electric car charging. When batteries are 85% charged, power from the solar PVs is redirected to hydrogen production by water electrolyzing. When charge level goes below 30%, for example after a couple of cloudy days with low PV-production, hydrogen is used by a fuel cell to recharge them. This type of batteries is sealed and do not build up gasses or detrimental coatings on the cells as ordinary lead-acid batteries tend to do. 

2. Producing, Storing and Using Hydrogen

Alkaline electrolyzer delivered by GreenHydrogen in Denmark. It produces 2 Nm³ of hydrogen per hour. It takes 5.5 kWh to produce and store 1 Nm³ of hydrogen with a caloric energy content of 3.3 kWh. To produce 1 cubic meter of hydrogen it takes 1 liter of purified and de-ionized water. From that amount of hydrogen 1.5 kWh of electricity and 1.5 kWh of heat is generated in the fuel cell. The fuel cell heat is integrated in the general heating system of the house. 0.5 kWh of the 5.5 kWh necessary to produce and store 1 Nm³ of hydrogen, goes to compressing it to 300 bars. Electrolyzer, fuel cell and compression system will be updated to newest technologies soon as the current devices are basically working prototypes developed by the suppliers in cooperation with Hans-Olof. The coming and more efficient electrolyzer from GreenHydrogen is of the PEM type. The new and more efficient Metal Hydride Compressor System from Norwegian supplier www.hystorsys.no has no moving parts and works by temperature differentiation. The new fuel cell is described in the section below. Annual production from the electrolyzer is roughly 3,000 Nm³ of hydrogen. 2,000 - 2,200 Nm³ will be used by the house for room warming, hot water, as well as household electricity needs such as ventilation, washing, cooking and lighting. Charging of electric cars is of course included. There is an estimated surplus of 800 – 1000 Nm³ that Hans-Olof plans to use for a Toyota Mirai (hydrogen fuel cell-electric car) that will run approximately 10,000 kilometers on that amount. Oxygen from the electrolyze process, half the amount of hydrogen, is vented to the outside air.

The hydrogen fuel cell is a working prototype by Swedish fuel cell maker PowerCell. It was developed specifically to this house as a mutually beneficial project allowing Hans-Olof to produce the needed heat and electricity in wintertime and creating a massive amount of data and experience for PowerCell. An internet connection provides monitoring and remote control of the unit. It delivers roughly 1.5 kW of electrical power and 1.5 kW heating effect. Two grey tubes on the left bottom side of the unit takes in cooling water and returns 65-70 C hot water. Red and blue cables top left deliver 48 VDC to the earlier illustrated inverter system. An electric effect of 1.5 kW may not seem impressive, yet when it runs 24/7 to charge the batteries there is always enough energy to meet peak demands such as car charging or the heating needs of the house – in fact all functions of the house. A new fuel cell is to be delivered by the same manufacturer and is now a standard product named PS-5. The “5” refers to kW – meaning it will produce 5 kWs of electrical power and 5 kWs of thermal power.

Temporary test storage facility for hydrogen to be replaced by a 12 physical cubic meters storage tank that will be built behind the big boulders seen in the background.

Foundation for the new 12 physical cubic meter hydrogen storage facility. Hydrogen will be stored at 300 bars. Current hydrogen production is projected to 3,000 Nm³ annually. The tank will be able to store a total of 3,600 Nm³ when production increases with the new electrolyzer and it will have the capacity to serve future increased energy needs by the house or hydrogen fuel cell cars.

3. Controlling and Monitoring Electricity

The main switchboard. Here Hans-Olof can control, time and program all switches and main plugs of the house. KNX products are used to build intelligent integrated building control solutions for the house. In the event of failure, the system switches in the redundant inverter system mentioned earlier. There is a total of 7 switchboards in the house. 67 permanent energy monitors log all electricity consumption. There is a total of 14 Kamstrup (make) energy monitors continually logging data from the water and heating system of the house. 10 different parameters from the weather station is logged. Hans-Olof accumulate all this data for simulation of energy flows and consumption patterns in energy usage projections and energy designs. He offers such projections and designs to people who wish to go off-grid like him.

An AC-power quality monitoring system is online with the Technical University of Luleå. Engineering researchers at the university are very interested in the performance and quality of an off-grid system like Hans-Olof’s. It’s a mutual benefit as the researchers contact Hans-Olof each time irregularities or unusual production-/consumption patterns occur – then they want to know if he did anything out of the ordinary like charging two cars at the same time, while vacuum cleaning, washing clothes, washing dishes all at one time, potentially stressing the system. The researchers monitor PV-production, overall house consumption, AC hertz rate, AC voltage and several other parameters. Beside assessing the impact of fluctuations in production, consumption and AC quality, the monitoring helps determine how the system handles the switching between running the house purely on PV in the summer daytime, night time/cloudy weather running on batteries and wintertime running on hydrogen.

4. Climate conditioning and water supply

Some of the central heating and thermal storage components of the house. In the background: Three 1000 liter tanks that store 35 C water for an outdoor snow and ice melting system under the paved driveway and yard. Plastic tubes are to be drawn extensively, 10 cm beneath the paved surface. The warm water circulates to heat up the above surface and melt away any ice and snow during winter. The system doesn’t run all the time – it’s sufficient to run it for while, whenever snow or ice has built up. The elliptical expansion container in front of the three large tanks will accommodate any over-pressures in the system. The two 400 liter tanks in the foreground contain 50 C water for the household (once a week it is heated up to 65°C to eliminate possible legionella bacteria. One of the tanks secures redundancy in the event of failure such as leak or when there is an extraordinary use of hot tap water in the house. 

Tubing prepared for the outdoor snow and ice melting system in the driveway and yard.

Some of the yard- and driveway area that will benefit from the sub-terrain tubular de-icing system.

The 13-kW geothermal Viessmann heat-pump harvesting energy from two geothermal boreholes extending 180 meters below the terrain surface. The heat-pump delivers room heating (floor heating) and hot water when the heat from the fuel cell not is enough from November through February. It heats the 3,000 liters 35 C water for the driveway/yard snow and ice-melting system as well. As it probably can be deduced from their appearance every tank is efficiently insulated to minimize heat loss or in the case of the drink water reserve to avoid condensation (seen partially far right).

Reserve drink water tank, 500 liters, with water purifier (blue container). In case the public water supply fails, the household has water for 3 days including water for electrolyzing. When in summer, each day with solar power counts to produce hydrogen and a water supply failure could mean the loss of dozens of Nm³ of hydrogen.

Supplying 500 square meter of indoor living areas plus an outdoor ice-melting system with heated water and heat-exchange fluids, takes its plumbing. Hans-Olof, as a former owner and technician in a refrigeration supply company for mobile applications (Termo King products, mainly for trucks and trailers), knows his plumbing and has done all tubing, connections, valve-connections etc., himself. I am very impressed with the quality and attention to detail in the system, even if I’m easily impressed, knowing very, very little about plumbing. The grey boxes with a rounded front, under the red handles, are Kamstrup digital gauges measuring the energy- (kWh) and physical (liters) flows for floor-heating, hot water circulation, towel dryers (bathrooms) as well as overall hot water consumption, also total water consumption from public supply is measured. Furthermore, there is a gauge for the house cooling (AC) using the geothermal tubing in the summer and lastly there is a gauge for the hot water production in the thermal solar panels on the roof. Two boxes with grey front and green casing are pumps handling hot water circulation in the heat distribution system. The grey bigger box between them is a 60-kW heat-exchanger for the outdoor de-icing system.

”Heat”-exchanger that captures frigidity from the geothermal tubing system running to 180 meters under terrain and uses it to cool the house in summertime. At this depth ground temperature is 6 to 7 degrees C all year round.

The central ventilation unit of the house – the heat from the outgoing indoor air is exchanged to the incoming outdoor air which then has a near room temperature when delivered. In summertime, the incoming air can be cooled from the beforementioned geothermal boreholes. 

Want to go off-grid yourself?

Now don’t worry if you feel a bit overwhelmed by the amount of technical information above. And furthermore, don’t worry if you think going off-grid demands an engineer in the capacity of Hans-Olof. With his background as an electrical engineer plus owning a company in the refrigeration industry as well as being a director of a wind turbine power company plus his current career as an energy consult, he has acquired all the necessary knowledge, know-how and skills required to pull off a project like this. Let’s also not forget that he has drawn in several project partners in the shape of participating suppliers and manufacturers as well as engineers from academia. That said, not to diminish his effort, it is in my opinion most impressive what he, his wife and project partners have done. An astonishing house has been built and it has been more than proved that off-grid is a possibility today even in a cold temperate climate like that of the Swedish West coast.

Consequently, it is no surprise that Hans-Olof asks me if it is ok that we interrupt my tour for a short while, after we had a nice lunch on his southward glass-covered porch. Another visitor has announced his arrival, it’s the director of a company manufacturing electric floor heating – being in the housebuilding and electric appliance business, the director plans a visit for himself and several business partners to Hans-Olof’s house. Today he stops by to get an impression of the house before he and his partners arrive for the grand tour.

Hans-Olof’s house has gained significant fame in the Swedish energy and construction sectors. IKEA, that we mostly recognize as a retailer in furniture and interior decoration, is a housebuilder too, mainly in Scandinavia. Partnering with constructors, they supply turn-key houses at fair prices – basically you order them by catalogue and pay with your credit card (a bit simplified).

So, what does IKEA have to do with Hans-Olof’s house? Well, imagine, they see business opportunities in off-grid and microgrid housing, on that account Hans-Olof recently had a group from IKEA top-management to come by and learn more about how to make an off-grid house. The fact that Hans-Olof has made a house of this quality and performance at a very attractive square meter price, has certainly raised curious eyebrows all over Sweden, and not only the housing industry is interested, more significantly the large energy corporations even more so.

Because of the latter’s interest, a large utility owner and power supplier in Sweden, is currently working on a 2.0 version of Hans-Olof’s house. Obviously, Hans-Olof works closely with the company adding his knowledge and skills to the project. The 2.0 version is a normally sized one-family house roughly 150 square meters. This time, building on experiences of Hans-Olof’s house, things can be optimized and in many cases done simpler, at an even lover square meter price. Not the least due to less redundancy and a less intricate heating and power infrastructure. 

The 2.0 version currently in construction is exactly why you shouldn’t give up on going off-grid either, just like only a few of us insist on building our houses completely by ourselves from foundation to roof – going off-grid will be a turn-key solution, offered by professional suppliers and constructors. And you probably haven’t built your Volvo or Hyundai yourself either.

Electrical and Telecommunications engineer - and off-grid expert, Hans-Olof Nilsson, in front of his 500-square meter off-grid villa 10 kilometers out of Gothenburg. Hans-Olof’s professional experience includes director of his own wind-turbine power company. Today he is the owner and director of the renewable energy consulting firm, Parkudden Energi AB. 

Hans-Olof Nilsson’s house in figures (annual):

Energy Production

•      Solar PV Power 22,000 kWh

•      Solar Thermal Power (heat) 6,500 kWh

Direct Energy Consumption

•      Solar PV Power        7,000 kWh

•      Solar Thermal Power (heat) 1,500 kWh

 Storage - Power to Gas

•      Solar PV Power 15,000 kWh is converted by water electrolyzation to 3,000 Nm³ of hydrogen

•      2,200 cubic meters are used to supply the house with heat and electricity in winter (November through February with negligible PV production)

•      800 cubic meters of surplus hydrogen potentially used for a planned hydrogen fuel cell car

A diagram showing the energy flows of Hans-Olof Nilsson’s off-grid house:

The diagram is made and generously delivered by Hans-Olof Nilsson

Hans-Olof has offered to answer any questions about his house and going off-grid via email: hans-olof@parkudden-gbg.se


The author wishes to thank Hans-Olof Nilsson for his kind invitation and subsequent generous sharing of information to make this article possible.