Solar inverters - where does the energy go when clipping?
The first law of thermodynamics states that energy can't be created or destroyed, so where does the excess clipped energy go when a solar array is generating 4kW on a sunny day but the inverter clips it's output to 3.6kW? Is the 400W of clipped energy lost as heat from the inverter? My inverter is in the loft so I've no idea how hot it gets on a sunny day.
Samsung 12kW gen6 ASHP with 50L volumiser and all new large radiators. 7.2kWp solar (south facing), Tesla PW3 (13.5kW)
Solar generation completely offsets ASHP usage annually. We no longer burn ~1600L of kerosene annually.
Posted by: @old_scientistThe first law of thermodynamics states that energy can't be created or destroyed, so where does the excess clipped energy go when a solar array is generating 4kW on a sunny day but the inverter clips it's output to 3.6kW? Is the 400W of clipped energy lost as heat from the inverter? My inverter is in the loft so I've no idea how hot it gets on a sunny day.
Einstein!! I think we lose it in heat in the inverter, don’t need to worry about that in the winter, solar is useless then. I’m thinking wind might be a better option if someone comes up with a decent device
Posted by: @old_scientistThe first law of thermodynamics states that energy can't be created or destroyed, so where does the excess clipped energy go when a solar array is generating 4kW on a sunny day but the inverter clips it's output to 3.6kW? Is the 400W of clipped energy lost as heat from the inverter? My inverter is in the loft so I've no idea how hot it gets on a sunny day.
It's a good question and one which I have asked myself. We really need a solar panel physicist to answer, I am a lapsed physicist but never really studied this particular specialty.
Firstly I doubt the panel does generate 4kW when clipped, because it's not correctly loaded, but for sure the solar energy does still hit the panels, so the question remains valid albeit slightly modified.
I think that when it is clipping the inverter presents less than a matched load to the panels, so I suspect some of the energy is absorbed by the panels resulting in them heating up more than would otherwise be the case. I could easily believe that, in addition, there is an effect on the reflectivity, but definitely don't know this to be the case.
As you say it has to go somewhere, the above seems plausible at least .
It's worth bearing in mind that solar panel efficiency has remained stubbornly around 20% for a decade more. This being the case some additional excess energy lost to heat is unlikely to cause anything to melt.
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
I understand that it gets dissipated as heat, mostly in the panels but some in the inverter. Since most solar power generates heat in the panels (80%) because they are only 20% efficient the extra heat isn’t a lot. We don’t need spurious heat though!
2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with it) open system operating on WC
In the solar panels.
On a nice sunny day, a square metre of panels would get 1kW from the sun. Of this we might expect 200W of electical power if a suitabel MPPT inverter is connected, and then 800W as thermal power warming up the panel itself. If you disconnect the panel, then the whole of the available 1000W will heat up the panel.
When the inverter MPPT backs off, it just leaves some of the power in the panel. If could choose the best MPPT point and to dissipate the excess power in itself instead - but no inverter will do this, as it would cause overheating and unreliability in a physically small inverter, while the panels are designed to be able to dissipate the thermal power.
Not that it's a good idea to leave panels in the sun unconnected - I think eventually they do get damaged this way for some reason.
Why do panels get damaged if not connected?
When they are normally in the sun, they get 800W/m^2 evenly distributed, and they warm up everywhere. Silicon doesn't like being super hot for too long, it will eventually degrade, but it's a long term problem.
I think if you leave a panel disconnected, you can think of the extra 200W/m^2 as actually electrically generated and then dissipated by the panel itself. The graph above shows that as temperature increases, the open circuit voltage of a PV panel drops - a positive feedback effect. So I would expect an unconnected panel to have hotspots where the current flows, and these will degrade it faster.
@robl thank you, makes perfect sense, and my wife is relieved to know the inverter isn't sat in the loft smouldering due to excess heat because of an oversized array.
Samsung 12kW gen6 ASHP with 50L volumiser and all new large radiators. 7.2kWp solar (south facing), Tesla PW3 (13.5kW)
Solar generation completely offsets ASHP usage annually. We no longer burn ~1600L of kerosene annually.
- 26 Forums
- 2,227 Topics
- 49.5 K Posts
- 233 Online
- 5,892 Members
Join Us!
Podcast Picks
Latest Posts
-
RE: New Fogstar 15.5kWh upright solution
😉 😉 Some folks get spare BMSs.. &...
By Batpred , 12 minutes ago
-
Solis S6-EH1P8K-L-PLUS – Why I Chose It and What I’ve Learned So Far
I ended up with a Solis S6-EH1P8K-L-PLUS (8 kW) hybrid ...
By Batpred , 15 minutes ago
-
Crazy if that is the case. It will surely be the norm ...
By JamesPa , 18 minutes ago
-
RE: Options on flushing my system
@grantmethestrength with your pragmatic approach and &#...
By SUNandAIR , 2 hours ago
-
RE: Samsung Heat Pump – Can't Activate TW2 Pipe Sensor (for Delta T Control)
@batpred For the moment I'm sticking with what I have, ...
By bubuontheweb , 3 hours ago
-
RE: Help me keep the faith with my air source heat pump installation
@jamespa ive found out today the Thermix plinth heaters...
By AdamK , 4 hours ago
-
RE: Electricity price predictions
Nice to be back on track! If we all had the interest, s...
By Batpred , 4 hours ago
-
RE: Say hello and introduce yourself
I think this is where we may differ. Nothing makes sen...
By JamesPa , 4 hours ago
-
RE: Daikin Octopus installation update - I saw my first defrost. 😍😂
Enable installer mode - 5678 Enter the Space Heating/...
By RadWhisperer , 4 hours ago
-
Is your installer MCS certified? If so, they should reg...
By Old_Scientist , 5 hours ago
-
RE: Havenwise App Help & Forum Support – Get the Most from Your Heat Pump
@hcas So the answer from Mitsu was: To Confirm you ca...
By bontwoody , 7 hours ago
-
RE: Air source heat pump roll call – what heat pump brand and model do you have?
Grant Aerona 3 10 HPID10R32
By MDG , 8 hours ago
-
RE: Testing new controls/monitoring for Midea Clone ASHP
I don't know! The Midea manuals and what actually happe...
By cathodeRay , 8 hours ago
-
RE: What crazy nonsense are inverter limits and why are they imposed?
If you’re interested in finding out which of your neigh...
By AgentGeorge , 9 hours ago
-
Hi, I have a Samsung ashp and I'm going in holiday. Can...
By richdorm , 10 hours ago
-
RE: Ripped Off: How UK Homeowners Are Paying Gas Prices for Wind Energy
It is a crazy situation. It also seems not enough 400kv...
By Batpred , 11 hours ago
-
RE: Rate the quality of your heat pump design and installation
More like Octopus wanted to fit a Cosy 6 at the end of ...
By RadWhisperer , 14 hours ago
-
RE: How good is the app support for your heat pump?
Yes. Personally I would only use a heating control app ...
By Batpred , 1 day ago