Using a hybrid nanoscale/macroscale model, we simulate the efficiency of a luminescent solar concentrator (LSC) which employs silver nanoparticles to enhance the dye absorption and scatter the incoming light. We show that the normalized optical efficiency can be increased from 10.4% for a single dye LSC to 32.6% for a plasmonic LSC with silver spheres immersed inside a thin dye layer. Most of the efficiency enhancement is due to scattering of the particles and not due to dye absorption/re-emission.