42

Reading here and a couple other places makes it sound like solar panel degradation varies widely. Manufacturing origin doesn't appear to be correlated to longevity or if it is, it may be opposite what we expect (China appears to do well). The general gist is that you'll lose a fraction of a percent every year on average. It's likely due to high energy ...


37

It's nothing to do with synchronization. It has to do with ensuring safety of utility workers. The inverter should be quick to disconnect in the case of a grid failure (seconds) wait a period of time (in this case 5 minutes) after the grid is restored before beginning to supply power out to the grid. See, for example this exchange (the "standard" in ...


31

60VDC is the cut-off for Safety Extra Low Voltage, or SELV, as spelled out in UL 60950-1. Besides being lower voltage, SELV circuits are also isolated from the mains by reiniforced insulation, which has specific spacing and materials requirements. In general terms, SELV voltages are ‘touch safe’, meaning that they don’t present a shock hazard with direct ...


29

Field-assembled battery hardware can't go outside of SELV without help The primary limitation on the DC bus voltage of most off-grid systems is indeed due to touch safety limits (60VDC/42.4VAC SELV limit), but that's not due to who's installing it. Instead, the issue is parts availability: lead-acid single cells and monoblocs of the sizes used in off-grid ...


23

The inverter has a software delay. This is intentional. It waits 5 minutes to make sure it is connected to a stable grid. An inverter could theoretically connect and go full power in seconds. But it doesn't. For example, if after a power failure, all inverters immediately went online a started outputting full power, the network would be overwhelmed and will ...


20

TLDR: Industries use industrial gear, and homes don't have 50kw demand. Really. This cannot be emphasized enough: DC is one nasty customer. It is easy to get complacent after spending a youth and a career working with docile, harmless 5-24 volts DC, or well-behaved 100 - 240 V AC voltages because of its frequent zero crossings. DC in that same range is ...


18

Almost all voltage regulators do have a path backwards from output back into its input because they are not designed to handle blocking reverse current. So your battery would drain back into the solar panel when there is insufficient light falling on the panel. For example, here's the internal circuit of an LM338 in your first schematic: (From here) While ...


12

Using the sun as energy source is actually one of the few reasonable ways to overcome the issues we are globally facing. The problem is the efficiency of conversion from sunlight to electricity (the conversion efficiency of photovoltaic modules is about 20%), plus the energy storage (Expensive, heavy batteries with limited lifetime obviously can't be the ...


11

Solar cells are a PV junction, basically a diode so they have similar characteristics. The voltage is dependent on the amount of energy received from sunlight and the amount of current drawn, so it is load dependent. Source: MPPT tracking Many solar panels are watt-rated. The generated power depends on lighting conditions, so either the current and/or ...


11

Just to address the "last essentially forever" part. Unlike some semiconductor devices which can work for half a century or more, solar panels don't get the privilege to be used indoors. This means they will suffer from UV and corrosion and will have a limited lifespan. It also should be noted that mass-produced solar panels are relatively new, which means ...


9

Good question. You are right that there is a contradiction there. How can you do maximum power point tracking if the load is not able to accept the maximum power? For a grid tie inverter, it is no problem because the grid can accept all the power that the solar array can produce. But what about a battery? What if the battery is charged already, or if the ...


7

I have an outdoor sensor (which will have to work in the winter on Poland, however, we usually have temperature much over -10 Celsius degrees) which needs 5V. The sensor operates 24 hours per day and consumes about 300 mA when working, for about 10 seconds every 5 minutes and less than 1 mA the rest of the time. Energy required: Operate: 10s in 5 ...


7

You are running your fans at up to 39 V, which is far above their rated voltage (12V, 24V). That will mean overheating and, eventually, burn out (provided they don't get destroyed straight away when you first connect them, as it happened to the 12V fan). You only have 2 options here: Buy a fan that can tolerate at least 39 V (which may be expensive or ...


7

Primarily current. Photons release electrons, which flow in the form of current. That current divides itself between two current sinks in parallel: a weakly forward-biased diode (i.e. the solar cell itself) and the external load on the terminals. That means the voltage you see on the terminals depends on three things : the characteristics of the external ...


6

There's nothing wrong with that until the first fault takes place. Then, you've greatly raised the probability of the system trying to kill you. With a grounded system, accidental ground connections do one of two things: (1) not make a lot of difference, because the fault is in the grounding part or (2) trip off the system until the problem is fixed. ...


6

As others have already noted, the question has both regulatory and technical aspects. This answer considers the technical aspects primarily, but includes some regulatory background information. Because regulations change and vary by locale, any future readers of this answer should look for the most current local regulatory information rather than relying ...


5

A large capacitor would work, yes. Just get something rated for more than six volts (I'd recommend more than twelve, a wide margin is a good thing to have!) and a large capacitance; the larger, the longer it will continue to run, assuming the panel was able to fully charge the capacitor before it was blocked. If you want it to run for a very long time, you ...


5

Correct - a capacitor would work. But you also need a diode to stop current going back into the solar panel when the solar panel is covered up. Some panels already have this though. Either way, you can add one, like this circuit, as explained here. I'd start with a 100,000uF capacitor or thereabouts. Just make sure that whatever capacitor you choose has a ...


5

The Diode is used to prevent backfeed into the cell from the battery. While daytime, the solar cell generates a voltage higher than the battery voltage, therefore current is flowing into the battery. When the cell is covered or it's nighttime, the voltage across the cell is 0V, so the battery, with it's higher voltage, would try to feed current into the cell,...


5

With something like solar power generation efficiency is a tricky thing to pin down. The micro-invertor itself may indeed be more efficient than the power optimizer, but it does that at a cost of much higher currents in the system. The latter translates into much more expensive wiring, connections, switching systems, and ultimately the micro-invertor ...


5

Here's a realistic curve for a realistic solar "panel" that you can get from a variety of hobbyist suppliers. This particular one has 9 solar cells (a 3x3 grid) wired up in series. Now, the blue curve represents the current vs voltage for the device. But what does it really mean? Well, assuming full sunlight (whatever that means for this curve) is hitting ...


5

My question is: will this 6m additional wiring cause a significant loss of final output? Is there a formula that I can use to arrive at a numerical figure? There is indeed a formula, but not in quite the sense that you seem to think. Wire has a per-meter resistance which is inversely proportional to the cross-sectional area of the wire, so asking what ...


5

An inverter can indeed supply a lower current than the solar panel rating without any system damage to the system. If an inverter is not supplying as much power as the panels can deliver it will simply draw less current from the solar panel. If you follow the IV-curve of the solar panel you will see that lower current from the panel allows the voltage to ...


5

Large buildings often run chillers during off-peak to make ice, then use the ice for cooling during the day. That’s a bit opposite of what you want, but it explains the principle of using phase change to store energy. The pump idea isn’t so dumb at all. It’s been used at larger scale in hydro dam projects to store energy during off-peak. Simplest thing? ...


5

The simplest is a shunt voltage clamp. The power from the panel is free, the panel is a high impedance output, and the power is low enough for a reasonable sized heatsink on the clamp to do the job. That way you lose no power at all while the output voltage is below the clamp voltage. Use a TL431 (or TLV431 the low voltage version) as the voltage sensor to ...


4

Start with a spec for power output and input, budget and complexity requirements so a suitable make/buy choice is easier. 5V & 3V Out, (5v main load) solar PV input _% tolerance 300mA for 10s every 300s or 10mA avg. 1mA standby current or 11mA tot. avg. @5V equiv 55mW avg. power consumption climatic: -10'C to ? low budget prototype ? sustained storage ...


4

You're confusing yourself with amps and volts, so it would probably be a good idea to just stick with watts, and convert at the end. You say your total load is 35 W, so you need 35 W × 24 h = 840 W-h per day of operation. I would recommend having enough battery capacity for at least 3 days of operation, or about 2500 W-h. (This would be 100 A-h at 24 ...


4

Yes, you will damage the battery if you charge at low temperatures (beyond the product specification). You can read this if you only believe research papers: https://www.researchgate.net/publication/282407632_Optimal_Low_Temperature_Charging_of_Lithium-ion_Batteries If you are using solar to charge the battery, then of course you could use solar power to ...


4

if I have PWM technology or a buck-boost converter that deems I need a duty cycle of 0.4 to reach the voltage I want... does that mean I don't generate power with my solar panels 60% of the time? Not if the converter is properly designed. You are probably thinking of a buck circuit that looks like this:- simulate this circuit – Schematic created ...


4

MPPT stands for Maximum Power Point Tracker. It tries to draw the Maximum Power from the panel at all times, and Tracks the panel's operating point as the amount of sun arriving changes. In order to stay operating at Maximum Power, the MPPT needs to have a load connected to it that can absorb safely all the power it produces. This means a sufficiently big, ...


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