We here describe and numerically simulate a new solid state active magnetic regenerative refrigerator (AMRR) aiming bulk applications. This system uses magnetocaloric materials and materials whose thermal conductivity changes with the applied magnetic field (H). Similarly to common AMRRs, H is moved gradually from the hot to the cold reservoirs to produce a cascade of Brayton cycles. This cascade increases the temperature span and can thus be used in bulk applications where the conservation of a cold environment is demanded. Our results show that by using gadolinium as magnetocaloric material (MCM) and H = 1 T, one can increase the temperature span from 2.5 K up to 11.5 K, an enhancement of over 450%. The optimization of such solid state system is here presented also in terms of frequency, operating temperature and time of contact between the cold reservoir and the MCM. (C) 2013 Elsevier Ltd. All rights reserved.