No. Solar PV does not provide a constant power as it is intermittent. To make it constant, you need to add energy storage.

Professor Yehia Khalil, Yale University, USA

Fellow of the University of Oxford, UK

If your question refers to loads with active power consumption independent to voltage and frequency variations in the supply grid, variable speed drives would be one example of constant power loads (in contrast to constant impedance loads, or constand current loads).

Moreover, directly connected asynchronous motors are showing little variation in active power consumption during voltage variations (as long as frequency remains constant), or in steady state low/medium voltage grids connected to the higher voltage levels via a transformer with automatic online tap changer that has not reached its limits yet.

If your question refers to the time characteristic of loads (intermittent, non intermittent), please disregard my answer.

Data center IT loads are fairly constant 24 hours per day. You may see a drop to about 80% of peak at night, but depending on the type of data center the load may in fact stay constant. 

Emergency egress lighting is also always on per code, but that's typically a small fraction of the total lighting power consumption. 

Hospital and laboratory fans are always on, and tend to operate fairly flat. Maybe turning down to 70% air flow at night depending on what controls are in place. Many older hospitals and laboratory fan systems are constant volume. 

Data Center internal processpor loads are reasonably constant with an anticipated SHR of 1.00

https://www.researchgate.net/publication/4155560_The_instability_effect_of_constant_power_loads

Conference Paper Stability Analysis of Microgrids with Constant Power Loads

Conference Paper Constant power loads in AC distribution systems: An investig...

http://www.elkraft.ntnu.no/eno/Papers2008/ISIE08_Marta.pdf