@Skewett 

You can consider add another EAP225-Outdoor, which can power on by PoE adapter. Like what we you have right now. The cable from PoE adapter to the device could up to 60m(Passive PoE adapter)/100m(Standard PoE adapter).

Two EAP225-Outdoor and Omada controller can build up mesh network. So the second EAP can wirelessly connect the first one. For more details, you can refer to this article.

Omada controller have software version and hardware version, you can select what's best for you. Software controller is free and you can download it on TP-LInk website. For hardware controller, you can check this model: OC200.

Just because the software was installed on your computer, so you need to run the computer(Software controller) the whole time. Just to make sure the mesh is activated.

I recommend you this just because they don't have outdoor wireless bridge, so don't have many other choices.

@Yannie 

Thanks for that info Yannie. 

Not quite sure how the second connector which is need to attach to my original Eap225 would get its power. 

I have a 12 volt supply only in my shed. 

I'm assuming that it would need a POE cable from somewhere to get its power? 

@Skewett 

Cant say i have ever used one of these and only thinking out loud.. but could the POE injector below be ran from your Solar Cell?  You might need to modify a barrel power connector for it however

https://www.amazon.co.uk/TP-LINK-TL-PoE150S-Injector-Adapter-Compliant-Black/dp/B001PS9E5I/ref=sr_1_3?keywords=poe%2Binjector%2B12v&qid=1640881399&sr=8-3&th=1