Earth Notes: 16WW Energy Systems Diagrams

Updated 2024-09-09.

Energy subsystem diagrams including microgeneration and storage at 16WW. #energy #microgen #storage

A central location for schematics of current (and former) energy systems at EOU Towers.

Not in this page:

Data collected by these systems: see the energy series dataset.
Devices run off these systems, eg see: On Setting Up a Raspberry Pi 3 Off-grid Server.

Note that extensive logging and processing of real-time and historic data from all energy subsystems is performed on Raspberry Pis.

Current Grid-tie Solar PV System

Summary: current capacity ~5kWp(e), ~4.5kWp(e) G83 inverters, AC-coupled, half east-facing, half west-facing, slope ~23° in each case.

Read more on the (first round of the) installation.

The electrical schematic (circuit diagram) for first 1.29kWp (2008).

The electrical schematic (circuit diagram) at expansion to 3.87kWp (2009).

The electrical schematic (circuit diagram) at expansion to 5.16kWp (2010).

20100415 3rd round schematic 5p16kWp excerpt — Solar PV 5.16kWp generation system as of 2010-04-15.

Enphase Storage System

Summary: current capacity ~5kWh(e)/~1kW(e), AC-coupled.

Read about the Enphase AC Battery Grid-connected Storage in Our UK Home then Enphase AC Battery #2 then #3 and #4.

Enphase Energy Storage Diagram — Generic Enphase (UK) installation schematic, courtesy of Enphase via Eco Partners. Note that 16WW for example has two separate PV subsystems with their own meters for separate Feed-in-Tariffs; the Enphase solar monitoring clamp fits on after the circuits merge after the meters to be able to measure aggregate generation. As of the end of 2021, 4x AC Batteries to ~1kW/5kWh are installed on the storage branch.

See also PDF original, courtesy of Enphase via Eco Partners.

Eddi PV Diverter and Thermino Heat Battery

Summary: capacity ~7kWh(h) down to 50°C, ~10kWh(h) total to cold ~10°C, 3kW(e) peak charge rate.

Unvented cylinder and Combi pre feed with solar Schematic 002 p2 SA — Generic schematic for (myenergi eddi) diverter, Sunamp Thermino and gas combi boiler in correct configuration for 16WW. (Extract from Sunamp PDF, with permission.) This autonomously deals with PV diversion when the system is spilling 'excess' PV generation to the grid. Some static adjustment of eddi parameters helps maximise grid-friendliness while reducing gas use in summer. Note that a dedicated RPi requests the eddi to provide boosts from the mains when carbon intensity is low enough and the Thermino is empty enough. This helps reduce gas use in winter while reducing the carbon emissions for DHW. The opportunistic use of 'excess' PV and low-carbon grid electricity to displace some gas use for DHW makes this a 'hybrid' or 'cross-vector' system.

The Eddi has one external current clamp deployed at our meter tails to measure total flow in and out of the building, connected to CT1 terminals. As of 2024-09-09 there is a spare/unused external current clamp connection, CT2.

Read more on the Thermino heat battery installation.

See the Eddi Solar PV Diverter Top-up Dataset.

Note that the Eddi and Thermino are partly managed remotely as of 2022-08 via Raspberry Pis to:

Provide overnight boost to the Thermino when grid intensity is low.
Pause diversion/boost in any minute when grid frequency is low.

Current Off-grid Solar PV System

Summary: current capacity ~1kWh(e) usable, ~0.7kWp(e) PV, DC-coupled.

main changes made; 510Wp 30Vmp in place — Off-grid PV system with storage as of 2016-08-05. [PDF]

Off-grid system notes:

The top set of panels at the west of house may be missing ~40W amorphous, ie should be 2Wp (amorphous) + 40Wp (amorphous) + 60Wp (multijunction).
The RPi2 is powered via an efficient hard-wired car USB adaptor (previously a stand-alone switching regulator), stepping the 12V down to 5V, with short leads to help handle demand spikes.
2021-09-03: the battery was replaced with a 220Ah Victron.
2022-09-09: 13:00Z: 100Wp panel was connected to the PWM side via a Schottky blocking diode.

Note that the Internet router is powered from the mains via a (12V) adaptor, which also has a 5V USB output. The adaptor also has a 12V-nominal input from the off-grid system, but preferentially uses 240V mains. When the off-grid system is in a good state, a 'dump' signal from the RPi disconnects mains from the adaptor with a relay, forcing the adaptor to draw from off-grid and act as a dump load. Thus the off-grid system acts as a huge UPS for the router too. The adaptor has at times driven more/other loads than the router. All recent 16WW routers have been 12V supply at ~1A; far more power-hungry than my MacBook Air as of 2023.

See Expanding and Optimising Off-grid PV for Mid-winter.

Merit Order

As of 2023-02 there is a 'merit order' of grid-tied PV generation use, best first:

Direct consumption in the house.
Absorption by the Enphase AC-coupled battery up to kW/kWh capacity (~1/~5).
Power-limited spill to grid (up to ~400W).
Diversion to Sunamp Thermino heat battery up to kW/kWh capacity (~3/~7).
Spill to grid (G83 limit / G59 was waived by DNO, so nominally unlimited but in practice ~4kW maximum).