Solar gets power even on cloudy days. It may not be as strong, but they certainly get energy through cloud cover. On top of that, using wind, hydro and other energy sources with additional battery storage helps to offset these issues. Transmission lines to better connect the energy grid EU-wide is also, clearly, a needed step, but that's not enough to deflect from making the investments in different energy sources. I worked at a solar company in Northern Germany, where they're not known for the most sunny days, and the solar we had on our facility was enough to power the entire old radio manufacturing building we owned, as well as over 343 households in the city. It's 100% possible. Ireland and the UK both have a lot of solar already, and they're perfect for wind generation. All it takes is the will to take the plunge (and they have been for years and years).