Category Archives: Allotment 44

Various news about Allotment 44

Jansjö Reading Light Conversion: running on 12 V, and never running out of light again, even in remote places!

How any would it be to have nice reading light at the garden house (or in the car), especially, a light without any smoke and hazard and hazzle like candle light! A light that keeps your eyes healthy. Well, at home, you can just use an IKEA Jansjö light for this purpose, which has a single 3 W LED installed.

All that is needed is a 12 V constant current board, LED driver. These are really cheap, so there is no need to build one yourself, you can just get it shipped from China directly, for a very reasonable price.

This board has a few nice components: 5 SS14 diodes (Schottky), 4 are used a bridge rectifier, 1 is used for the buck converter. There is a 47 Microhenry inductor, a 220 Mikrofarad (25 V) capacitor – and, the magic switch and regulator, a PT4115 device.

The PT4115 features a pretty straightforward design. It’s a step-down converter, can can drive over 1 Amp of current. The board I am using has a 0.22 Ohms current sense resistor, i.e., it is set to 0.1 V/0.22 Ohms = 0.46 A of current. This is plenty to drive the IKEA lamp.

The lamp itself will remain completely unmodified, just using a socket to connect to the original plug (which used to plug into a mains-powered LED driver of similar current rating). The connection to the 12 V system of the garden house is done via a “cigarette lighter” plug.

To protect the driver board, all sealed up in hot glue! It’s not perfect, but it works!

Finally, not much more to say, it works just fine!

Solar Upgrade: Another 140 (40?) Watts

Summer is already at its best, but unfortunately, my solar system (of the garden house) is not performing as it should. The battery is never at the predicted state of charge, and somehow, all performance is looking pretty much off the earlier predictions and calculations. Why is that? Well, first, checked the charge controller, but all seems fine. Next, the two solar panels (about 100 W each), and to my greatest dissatisfaction, one of the modules is only giving 8 Volts, rather than about 16-18 Volts, in full sun, and with no load connected. That’s not good.

A few days later, a big, flat box arrived –

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– with a 140 Watt polycrystalline solar panel! Quite affordable, just about EUR 115.

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Quite beautiful to look at, especially, at the current and power information.

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Mounted it on the roof – there is still plenty of space, but one module will be good for now.

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Below you can see both the new and old modules. One of old modules (the polycrystalline module) has been disconnected – I will leave it on the roof for now, at least it is shielding it from the rain.

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Updated simulation – with an assumed, generous power usage. Seems we should be good even in winter. But let’s find out later this year!

solar simulation

Weber Q100: BBQ repair and Q-burner

These days, fully occupied with workshop renovation and extension, and with spring gardening activity. One item that can’t be missed in an allotment garden definitely is a BBQ. Well, there are 2 coal-fired BBQs already, why not add a (gas powered) Weber? Only downside, these come at a quite significant price tag, and most times we will be using the charcoal grills anyway. But recently, opportunity came along, by the kind offer of a friend who upgrades his Weber, and was looking for a new home for his Weber Q100, albeit, in non-working condition (“it doesn’t heat up properly”).

This is the full view, including the stand, and a standard propane bottle already connected.

Based on the data of the Q100, no need to run on special Weber gas, or Weber gas cans.

sdr

This is the gas regulator I am using, just ensure it is 50 mbar, and has about 1 kg/h max flow. That’s plenty for the Q100.

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After 1st inspection, it is clear that the burner (stainless steel pipe in Q shape with many holes) is not in good condition. Several outlets blocked up. Usually, first recommendation is to scrub with a good stainless steel brush, WHILE the burner is in operation. This will burn away all grease and particles. Tried, but a bit too much residue to make this work.

Replacing the burner – certainly, an option, but costly, and these Q burners appear to be in short supply as spares.

q100 brenner

For cleaning of the Q-burner, following recommendation:

(1) Remove Q burner from BBQ
(2) Clean thoroughly with a wire brush especially at the side that has the holes
(3) Clean inside, by knocking on it with a piece of wood (brown dust will fall out), and with any kind of small brush or wire you might have at hand.
(4) Put in dishwasher to remove as much grease as possible, clean with some methylated spirits and/or acetone. If not properly de-greased, you will have trouble with the next step.
(5) Check all the holes by using a 1 mm twist drill. Make sure not to enlargen the holes but just to remove and solid residue.
(6) Clean with pressurized air or similar.
(7) Mount again.

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Also make sure to clean out the “venturi” section and wire mesh at the inlet.

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Mhh, still no good flame. Seems the Q100 is not getting enough gas. You need to check the orifice.

(1) Remove the gas inlet unit (the assembly with the knob to regulate the gas flow, two screws).
(2) Remove the orifice (which has a hex outside, usually, glued in with some Locktite). Don’t break any of the plastic parts.
(3) Clean out the orifice with air. No wire! Check visually.

To avoid blockage of the orifice, it is advisable to never connect a dirty gas pipe to the Q100 (some spiders might have crawled inside), and to cover the gas inlet of the Q100, if you need to remove the gas pipe for some reason. Best method is to leave the gas regulator and pipe/gas tube permanently connected.

q100 orifice

Now, after all this work, the Q100 is on flame again. All burning nice and blue.

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Just after a minute, already heating up quite a bit. Now we have to put it to a real test next weekend.

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Solar Power to Electricity: Around-the-year analysis

Undoubtedly, a garden house will need most electric power in summer, because this is the time where you have long, worm evening. In winter, if you really want to stay in the garden house, better to switch the lights of and hibernate anyway.

So, how much yield (kWh) do you get from a photovoltaic system, located in Ludwigshafen, Germany? Well, there are very precise calculation models around, based on actual data. You only need to know the location, inclination and direction of the solar panel (and hope there is no shade!). For my location, about 8.4080 East, 49.4897 North, Orientation 192 degrees (SSW).

Then you go to Photovoltaic Estimation, and type in these numbers (select “stand-alone PV”).

Also, you need to know the Wp rating of the the photovoltaic cells. In the given case, we have 1 module “Siemens M55” (this has been around for a long time, datasheet of a current equivalent Siemens SM55 Datasheet), and a second one, quite similar, but slightly larger (need to find out the model number), all in all, 120 Wp estimated. The system also has lead acid batteries with total of 190 Ah capacity (C/100 discharge rate), but I just assume 170 Ah.

solar siemens m55 data

Feeding the various data into the calculator, it’s a really great tool!

garten solar calc tool

Total energy that can be harvested, per day:

garten total pv energy

Now, lets be wasteful and consume an average of 400 Wh per day. That’s enough to run some lights, and a sizeable fridge all day.

garten 400 wh

garten 400 wh graph

A bit more conservative scenario, running an energy-efficient small fridge, and some lights (sure, you can also charge some cellphones or run a laptop computer).

garten 200 wh calc

garten 200 wh graph

Now, lets check if the battery will running low – just changed the discharge limit threshold to 20%.

garten 200 wh 20pct cutoff

Still good, seems like we will have plenty of electricity during summer the summer months – in winter, we will just switch off the fridge, anyway, it is the best time for hot rather than cold drinks.

Standalone Photovoltaic System: lead acid energy storage cost

For any standalone photovoltaic system, a battery is essential, because electricity is most needed when the sun is not shining. With all the many battery types around, lead acid type batteries still appear to be the best choice for a low-tech system in a harsh environment like a garden house.

First, we need to understand that the cycle life of lead acid batteries strongly depends on the degree of discharge (DOD) per cycle. I.e., a battery rated as “120 Ah” would be only discharged by x% of its total capacity, and last much longer than with a full discharge every cycle.

This is the battery we are talking about – quite impressive packaging, no wonder, because there is liquid sulfuric acid inside!

mde

It is a N120S NRG Solar 12 V, 120 Ah, “Deep Cycle” battery. About EUR 75 if you buy it a the right spot.

mde

Some average life cycle data vs. DOD% for lead acid batteries.

solar cycle life2

With cost, DOD%, etc, you can easily calculate the total energy stored over the cycle life of the battery. Time-wise, the battery can last about 8 years, at least according to the manufacturer’s data. So, with about 100 cycles maximum per year, one cycle per day (unless earth rotation will pick up dramatically…), no particular useful life beyond 800 cycles.

solar cost

With these data, it is quite clear that for the type of battery brand I am using (which is not the best most expensive super grade solar battery), running at 20~40% DOD will give quite OK life time expectancy, and cost even lower than domestic/grid power here in Germany, at least with the paid-off solar cells and charger.

solar cost per kWh vs DOD

Sure, measures will need to be taken to avoid full discharge of the battery in winter, e.g., by disconnecting all major consumers, and just allow for some LED or fluorescent lights, and maybe, a few cellphone chargers.

Allotment 44 (Parzelle 44): Gardening, rather than soldering!

In these days of global trade, endless supply, and magnificent business opportunities, why not take a step back, and spend some time preparing the ground, in the the literal sense. This time of the year is great for such activities, and after several months of winter, working outside in the fresh air is certainly a recipe to keep good health and to enjoy life with family and friends.

Long story short, after passing the formal application procedure and test, we are now the proud owners of a garden allotment, number 44. In German, Parzelle 44 (Kleingartenanlage am Riedsaumpark, Ludwigshafen am Rhein, Germany).

solar orientation plan

The last owner could not maintain it for the last 2 years, so, it is in a bit desolate state, but nothing that can’t be fixed, and with these pictures being a few days old, it is now looking already much better.

This a general view of the allotment, 300 square meters total, a bit over 3200 square feet.

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dav

It also features several buildings: a garden house (stone-built, dry, and in good shape, just needs a bit of paint), a summer kitchen and workshop (wood frame construction, behind the house), and a tool shed (other side of the house), as well as a rather spacious patio. Enough space to stay there over the weekend, or to have extensive BBQ with a whole soccer team.

sdr
sdr

Needless to say, it is a garden house, there is no connection to the power grid, or to a gas pipeline – at least, we have tap water! All else will need to be served by propane bottles, and by a photovoltaic system. Sure enough, no need to upgrade this to a too high level, with the main residence just a 10 minutes walk away, and we don’t want to defeat the purpose of it, to be a bit close to nature!

Stay posted!